A few days ago, Bashiok confirmed that the Firelands raid will not be a part of patch 4.1. So what can players expect to see in the update? Zarhym has posted a list of the featured content:

• Zul'Gurub revamp
• Zul'Aman revamp
• New level-85 Stranglethorn quest line (phased) leading players into the troll dungeons
• New tier of Heroic dungeon gear (epic item level 353) to give players a slightly bigger boost going into raids for the first time
• New & updated flavor items, vanity pets, and mounts
• Guild Challenges (new guild quests)

The guild challenges are a new addition and Blizzard hasn't posted any details yet, although Zarhym did hint over the weekend that Blizzard is currently preparing information on the feature.