"Cataclysm will change the face of Azeroth as you know it" - Chris Metzen
See the table of contents for the major points of the expansion.
All old world zones will be revamped in some way during Cataclysm. Chris Metzen was quoted as saying "No part of the world has been left untouched. Well, except maybe Westfall." Indeed, MANY of the old parts of our familiar world have been changed horribly by Deathwing's cataclysm. As a result, the entire leveling experience has been altered for 1-60. Zones will cover a smaller range of levels, and many zones are drastically altered as a result of tsunamis, heavy storms, volcanoes, and other effects.
However, part of the other driving purpose behind the revamp was to allow flying mounts in the old world. They will now be available. Additionally, no-fly zones are gone, including in cities.
More specific known changes include:
Blizzard has promised that questing, quest rewards, and everything else we remember about the old world is gone, replaced by a newer, darker, but improved! version of the world. This expansion also promises to put the war back in Warcraft -- the newly revised content will place a greater emphasis on the struggle between the Horde and the Alliance.
Zones are no longer the level ranged we previously remember them for. For example, the Undead leveling progression would be Tirisfal (1-10), Silverpine (10-20), Hillsbrad (20-25), Arathi (25-30), Hinterlands (30-35), Western Plaguelands (35-40), Eastern Plaguelands A (40-45), Eastern Plaguelands B (45-50). It would seem that the Barrens is not the only zone being split it half.
The level cap has been raised to 85.
To accomodate players, there are at least seven new zones. Presented at Blizzcon were:
Except for the newbie zones of Gilneas and The Lost Isles, these are for levels 78-85.
New dungeons include:
Deepholm is the elemental plane of earth where Deathwing comes from. It is intended to be the hub zone of the expansion, where you can travel from Deepholm to any other new zone and back.
Sunken City is an underwater zone. At Blizzcon, Tom Chilton promised to keep it from being "annoying". It is connected to the Abyssal Maw, which is the gateway to the elemental plane of water. Abyssal Maw will have two separate wings. It is a non-linear 5-player dungeon.
Underwater combat will occur on the sea floor as though it were on land. Blizzard is planning on introducing Underwater Mounts.
Uldum will have a new titan-created race called the "Tol'vir". It will contain at least two dungeons, and is Egyptian-inspired.
Uldum: Halls of Origination will have 7 bosses. It is an indoor 5-man. There will also be an outdoor dungeon. Allegedly, it contains an ancient Titan superweapon that many forces are trying to obtain.
Ragnaros has returned from the plane of fire. Hyjal will be about a conflict between the restored Ragnaros, and the returned Malfurion Stormrage.
Grim Batol has become the new base of operations for the Twilight's Hammer, who serve Deathwing. It will be located within the Twilight Highlands. The red dragonflight has been pushed back to the edge of the Wetlands.
The elemental plane of fire is home to Ragnaros and Sulfurion Keep. It is a raid zone.
New dungeon within Blackrock Mountain. It includes lots of experiments from the Twilights and is considered an offsite base for Deathwing and his cultists.
Blizzard has opted to add two new races to the game, Goblins for the Horde and Worgen for the Alliance. Additionally, many new class combinations have been made available. However, there are no new classes or hero classes in Cataclysm.
Lots of Wrathgate-style cinematics will be incorporated for the new races. The zones will be similar to the Death Knight zone in style, using phasing to advance the internal storyline, however they will be playable for all characters.
The playable goblins are not associated with the Steamwheedle Cartel, and in fact are disassociated from them. These goblins have been shipwrecked on "the Lost Islands" due to Alliance involvement. They have chosen to join the Horde as a result. Actually, the goblin characters begin as neutral and will gain their allegiance to the Horde as they move through the initial starting zone.
Goblins have hand-built drag-racer style mounts. Goblins can be any class besides druid or paladin.
The Worgen were "created" by Arugal, the mage of Silverpine, who summoned them to this world from their own. Initially they heeded his words and fought against the Scourge, but eventually they turned on him and everyone else. The true Worgen left many humans, including the majority of the kingdom of Gilneas, cursed with a werewolfism that has rendered them with their current form. Worgen can be any class besides paladin or shaman.
Chris Metzen has called the Worgen the "Wolverine" of the Alliance. They were chosen because it was believed that the Alliance needed a more bestial race, which was common for the Horde, but absent from Alliance members. Tom Chilton fully expects people to be saying "World of Worgen-craft" before long.
New classes are available for existing races.
The level cap will be raised by five, not ten. Instead, there will be a focus on a secondary means of leveling, called Path of the Titans.
You will receive an additional talent point per level, however there will be no additional row of talents. However, the talent tree structures will be completely revamped for all classes, as any talents that provide passive buffs will be edited out of the talent trees and moved into the mastery system.
Path of the Titans has been revealed to be a system similar to Everquest's alternate advancement system. There will be no additional tier of talents added to the game, however you will receive your alloted 5 talent points for the increased level cap.
The Mastery system adds passive bonuses related to your primary talent tree as you spend increasing numbers of talents in it. The goal with the system was to encourage players to take more fun and interesting talents, rather than strictly the bestest bonuses available. Talent trees themselves will no longer provide any kind of passive bonuses.
Guilds now have the ability to level up. They range from level 1 to 20, and advance via raids, dailies, bgs, etc. Guilds will get talent trees as they level up, with access to things like cheaper repairs, lower durability lost, or mass resurrection.
Guild currency is gained through guild experience, and is used to pay for heirloom patterns (bound to guild), among other things.
Profession caps will raise by another 75, to 525. Blizzard is adding a new secondary skill, Archaeology.
It will be possible to use more than one gathering skill tracking ability at a time. There was discussion about possibly gaining multiple skill points each time an activity was performed that could increase profession skill; this was discussed within the context of crafting skills, but was likely to include gathering skills to aid in smoothing the leveling curve.
Engineering is going "back to its roots" to add more convenience items, and gadgets with catastrophic failures.
Big changes were rumored for Fishing.
From Blizzard directly: "Through this profession, all players will be able to find ancient and valuable artifacts sometimes providing them with unique rewards. Those who master the profession will be able to explore our new Path of the Titans system, which allows for greater character customization."
Archaeology is considered a gathering skill, and can do things such as aid in collecting vanity pets, let you instantly travel to a dungeon thanks to a secret passage you discover, earn titles, and find recipes for other professions. There is a possibility that it may also include the crafting of staves and crossbows, although Blizzard was going to save this possibility previously for a future woodworking skill; if they follow through with this, bows may be added to engineering.
Once mastered, players will be able to collect Titan artifacts, which are exchanged for the currency for the Path of the Titans system.
Reforging is an additional skill that will be given to all crafting professionals. It will allow you to reduce one stat on an item, and add the points to another stat not already on the item. Items are reforgable multiple times. A character can only reforge items appropriate to their profession. (A blacksmith would reforge plate armor, not leather.)
With the 5th anniversary of WoW, Onyxia's Lair was revamped for the present level cap. With Cataclysm, old instances will have a new heroic mode for level 85, including Deadmines and Shadowfang Keep. The Onyxia fight will contain new versions of old loot (including Quel'serrar,) and the updated fight will have a similar flavor to the old version, but not identical.
Deathwing has returned. He seems to be the pivotal character in the expansion. Indeed, he is the one that has caused the "cataclysm." Although once he had special metal plates fitted to his body for additional protection, now apparently that is all that keeps him together.
One of the major places adventurers will have to travel is to the planes where the elemental lords had formerly been trapped by the Titans. Thanks to Deathwing, these locations are now unsealed, and notably Ragnaros is extremely unhappy.
Other significant players include Thrall, Garrosh Hellscream, Varian Wrynn, Genn Greymane (Gilneas ruler), and Azshara
3 battlegrounds are expected to be added to the expansion, including the "Battle for Gilneas," where players try to control as much of the city as possible. Tol Barad is an outdoor PvP zone described as "A combination of Wintergrasp PvP and Isle of Quel'Danas style dailies."
New battlegrounds will include rated team play. Rated Battlegrounds will allow you access to the same level of gear as Arenas! You will also gain arena points for winning rated battlegrounds, limited based on your previous week's rating. The old honor titles will return to battlegrounds once again.
New arena maps are also promised.
Hunters will use focus rather than mana, and ammunition will no longer be a consumable. Focus regenerates automatically with a maximum of 100, like energy, and will regenerate slightly faster by using steady shot. It is expected to regenerate on its own more slowly than the rogue's Energy. This change means there will be many fewer cooldowns as a result, and hunters no longer care about Intellect. Blizzard is still deciding how best to implement ammunition changes.
Pets are going to be completely immune to boss AE, possibly as soon as 3.3. When they review pets, they will do it one species at a time.
Shamans are meant to be good AE healers. The team will be looking at this.
Warlock shards will be incorporated into the UI. They will no longer be an inventory item; rather, you will get 3 shards for use per fight. They are strictly for in-combat use, and regenerate outside of combat. There is a chance Demonology may provide a bonus of having a fourth shard. The only spell that will cost shards is called Soul Burn, which has a 30 second cooldown and empowers the next spell cast. An empowered spell will have some kind of bonus effect, which depends on the spell cast; for example, empowered Fear would be instant.