Things I will do:
1. Level my Priest to 70, grab a swift flying mount and go for heroic instances and raiding. The preliminary plan is to stay in the instances as much as possible, for three reasons: first, to avoid outdoors spawn camping problems , second because the better drops are from instance bosses and third to max out faction gain from killing mobs. Quests that don't offer upgrades over current gear will be left for later, to ease the road from Revered to Exalted.
2. Along the way max out herb/alchemy, I've got about 2000 herbs stockpiled so any levelling that can be done on 'old world' herbs will not be a problem but I expect it will be mostly on Outland herbs. Fishing will probably be maxed out as well since it's proven very profitable in the past. First Aid and Cooking I'm not worried about, unless Blizzard changed their approach I expect they'll be maxed out with little effort.
3. Get all alts through the Portal, unlock their tradeskills and gathering professions so they can level up to 375. Start the 'factory' so to speak :-) Do gathering runs during off-hours to minimise competition for spawns and make max use of any cooldowns in each tradeskill.
4. Pick which character will become Jewelcrafter (hunter, rogue or warlock). I'm leaning towards the warlock dropping Goblin Engineering and becoming Enchanter/Jewelcrafter for double benefit from getting rep with factions, but it feels harsh to drop Engineering on the character which has most of the rare schematics. Realistically the 'old' 1-300 engineering will be useless though as it's all going to fizzle against high level opponents. Whichever character I pick will be the first alt I level up to 70.
5. Level up the other alts. This will be very casual, probably whenever I'm looking for a change of pace or somebody wants a specific class for something. Also they'll get some XP while mining or herbing, maybe also if I decide they need some rep with a faction for their tradeskills. Maybe the Rogue will be levelled for easy cash farming and stealth runs if there's good places for it.
6. Take a break. Go to Italy or France for a week and enjoy life away from work and Warcraft.
Things I will not do:
1. Create another alt. 1-20 is easy and might be fun in a new zone, but 21-60 would be the same old same old. There is some nice new racials but they are not enough to justify starting over. If there was a new non-hybrid class I might reconsider, but not for race alone.
2. Forget that my girlfriend exists! Time will be set aside for things that are more important than games.
3. Spend money on buying ridiculously overpriced schematics on the AH. Lesson learned from last time around, if I can't clearly see how to make the money back I'm not buying.
4. PvP. Unless the Eye of the Storm turns out to be brilliant or there's a reward that would be awesome in PvE raiding then I don't expect to do any more than the most casual PvP.