A summary of what we know

[Renzokuken]

What we all know
-Level cap increased to 80
-New area of content is situated in northrend.
-Siege weapons/Destructable buildings in BGs/World PvP
-Death knights
-NEW DANCES
-A little more character customization

Northrend related
-Flying mounts work but are disabled until 78 or 80
-Undead related(duh)
-Dalaran is the new shattrath, mages moved it back to daralan
-There is 2 "starting" areas to northrend to ease release day stress and to give a different leveling feel
-Naxx will be a new 25 man, retuned of course.

Death knights
-It will not delete your current character and turn it into a death knight
-You do not need to be a paladin
-Quest chain similar to warlock mount chain to unlock rolling of a death knight
-Starts at a high level(60, 70, maybe 80)
-Wears plate, tanks/dpses with 2 hander
-Rune resource system, not much info on it yet.

PvP related
-New BG is right now is 15vs15
-Twink arenas are in consideration
-A zone or area dedicated for World PvP with siege weapons
-Guild battlegrounds
-Changing of BG size as an option(15v15 AVs, 20v20, etc)
-Regroup queuing for AV
-AFK fix for AV and other BGs, a report feature that will ends up in a debuff that will say you need to get into combat or you will get no honor within X amount of seconds.

Class related
-Spell damage will be put on healer gear, so classes can do stuff in their hard earned purpz
-Croud control for shamans between 71-80
-Fear ward for all or similar spell
-Mana problems are being looked at for some classes, mainly priests.
-Hunters getting buffed somehow to help close range combat in 2v2,3v3
-Mage will get a soulwell type spell for food/water
-Ret pally stat distribution is being changed relying less on spell damage
-Totems on shamans is being looked at to compare with paladin auras, but blizzard still wants them to be different

Misc, Gimmicky ****, stuff I'm too lazy to categorize
-Engineers can make flying machines
-Legendary ranged for hunters and possibly others
-Engineers will be able to make out in the world mailboxes when it is no longer exploitable.
-The gear transition from TBC to Northrend will be smoother due to less of radical change in stat itemization(So shut the **** up)
-Players will be able to interact with arthas, he will be stirring up trouble for you in northrend
-You may get to fight the lich king but not arthas
-No new playable races
-Building in gear management and threat meters

Stolen from SomethingAwful. Figured this would be a good place to pool what we know.

[CelestialBadger]

Croud control for shamans between 71-80

OMG SO OP

[SouLess]

They didn't say that for sure, they said they were looking into it.

But yeah, pretty OP

[jd-inflames]

Wait wait wait...NO ARTHAS?!?!?!?!