This is a list of everything I know about Call of Duty: Modern Warfare 2 at this point in time:

(updates to this list are in… whatever this color is)

General Info:

• Release Date is 11-10-09.  All major retailers are taking pre-orders.  Amazon in particular is offering release-day shipping and $10 credit towards a future purchase.
• It’s being released for Xbox 360, PS3, and PC.
• There are three editions, for the console versions at least.  Regular, Hardened, and Prestige.  Regular is just the game.  Hardened comes in a steel case with an art book, “custom art”, and a code to download Call of Duty 1 (HD) when it gets released for XBLA and PSN.  Prestige edition includes all that the Hardened edition does plus “fully-functional, wearable, adjustable Night Vision Goggles with indiviually numbered and engraved collector’s stand.”  The editions are priced $59.99, $79.99, and $149.99, respectively. I’m not sure what the editions will include for PC or what the prices are.

General Gameplay & Engine:

• Enhanced Call of Duty 4: Modern Warfare engine, running at 60 frames per second on consoles.
• A new live-patching system will allow Infinity Ward to directly update the game’s data files, bypassing lengthy console certification patch processes (and potentially fixing multiplayer cheats & exploits much faster).
• Some vehicles will be “interactive” (drivable), such as the snowmobile, truck, and tank.  You can shoot a pistol with your left hand while driving (at least with the snowmobile),
• You will be able to swim and go ice-climbing.
• Confirmed weapons:  ACR, AK-47, AT4, AUG HBAR, FAMAS, SPAS-12, USP.
• The game will have “customizable weapons” (possibly more customizable than CoD4, but maybe not).
• One of the weapon customizations will be a “Heartbeat Sensor”, which is an attachable motion-tracker, a la “Aliens”.
• There will be a controllable, motion-tracking auto-turret, a la “Aliens”.
• The game will have riot shields.
• Apparently you’ll have the ability to throw and stick a “Semtex” to enemies, a la Halo’s plasma grenade.
• “We go for authenticity not realism,” Zampella told Official PlayStation Magazine. “We’re not making a sim, we’re making entertainment. We want it to look real like an action movie.”
• (7/30) The HUD will be smaller on-screen and have a new compass.

Single Player:

• Linear, longer story mode with opportunities to take alternate paths through levels.
• Levels will be “bigger” than those in CoD4.
• Levels settings include: Rio De Janerio (Brazil), Russia, a military base in Kazakhstan, and a desert area in Afghanistan.  Level missions include: an oil pipeline stealth scuba operation, an oil tanker attack, a Siberian operation (with a snowmobile), and a helicopter assault.
• Special co-op mode called “Special Forces”. Co-op missions are not tied to the main campaign’s story, but may provide alternate viewpoints.
• Co-op levels include a snowmobile race, a battle alongside U.S. Navy SEALs, and fending off a wave of 50 enemies at once.
• Fewer infinite enemy respawns that are only stopped by passing an invisible trigger line.  The game engine uses a “dynamic AI,” which has replaced the respawn system and allows enemies to act more independently. These “smarter” enemies are designed to actively seek and drive the player forward through a level, and can break away from set behaviors such as following a designated route in order to attack more quickly. The player cannot depend on an enemy being in the same location because enemies will behave differently each time a level is played.
• Stealth will be a viable gameplay option (no more enemies with x-ray vision).
• CoD4′s Captain ‘Soap’ MacTavish returns as a non-playable character.
• Ken Lally (Resident Evil 5′s Wesker), will be a voice actor.
• (7/30) Co-op will be 2-player only.

Multiplayer:

• Xbox 360 will be getting timed exclusivity on two map packs; PS3 owners will have to wait 6-12 months.
• Killstreak loadouts will be customizable with new unlockables (so, instead of always getting UAV radar at 3 kills, air strike at 5 kills and a helicopter at 7 kills, you’ll be able to choose what you want and when).
• There are 15 killstreak loadout unlockables, including AC130 cannon fire at 11 kills.
• You will be able to man the guns of AC130 (with thermal vision) during multiplayer.
• You get bonus XP for killing a player right before they get a streak (“Buzzkill”) and for getting revenge on them (“Payback”).
• It is apparently possible to earn 2300 XP with a single kill.
• Multiplayer will “highlight exceptional players and reward heroic actions.”
• (7/30) 4 factions. (Possibly “US Army Rangers”, “British SAS”, some sort of middle-eastern faction, and “Russian Spetsnaz”)
• (7/30) The AC130 will have a time limit (30 seconds?) and have 3 different guns you can switch between.  You can turn thermal imaging on and off.  The gunfire can destroy parts of the environment.

Some HD gameplay videos you should watch:

• Gameplay Trailer
• 9 minutes of Gameplay footage
• Multiplayer AC130 Video (if you only watch one video, watch this one)
• (7/30) Multiplayer AC130 Video w/ GameTrailer’s “Pop-Block” additional information

Sources: Planet Call of Duty, Wikipedia, Multiplayer AC130 YouTube video, GameTrailer’s “Pop-Block: Multiplayer Video.