NEWS UPDATED on June 11, 2010NOTE: NOT 100% confirmed yet!Just recently got some info on the online perk/weapon system, much thanks to vT Pikachu aka Chaidez...
Copy + pasted info straight from
http://callofduty.com/board/viewtopic.php?f=73&t=242924&st=0&sk=t&sd=a&sid=3ddb5121430d0170ecfc57f74aec9c76This is a list of the new improvements/ features for the game that are mentioned:
1) You only get two perks in mutliplayer, and this combination of perks determines your third perk.
2) There is a new armour system, e.g. Cold-Blooded and juggernaut are armours you can wear (not much detail given on this).
3) The FAMAS returns, but is no longer a 3-round burst weapon. Instead it is full-auto.
4) There is no M4. Instead another new gun mentioned seems like it will take its place, the SIG Commando.
5) Other new weapons confirmed include the RPK, Skorpion and MAC11.
6) There is no commando perk. (:])
7) The scavenger perk is included, but no longer replenishes equipment.

The One man army perk is also not included.
9) The highest killstreak reward (at this time in devlelopment) is 15.
10) There is no emergency airdrop, but there is a care package.
11) As confirmed before, killstreaks will not stack. For instance, if you get a 5 kills without dying and receive your killstreak reward, the kills you get with that killstreak reward will not count towards your next killsreak (e.g. 7 kill killsteak). You will have to get two more kills, in that instance, by other means to receive your next killstreak.
12) You can sprint to prone in the current build of the game. Basically this means you can dive straight on your belly after sprinting, instead of having to stop, crouch and than go prone.
13) The tactical knife is gone, while a new knife is being introduced: the ballistic knife. This is a knife that has a spring that can shoot a blade (in real life, not necessarily in the game).
14) The claymore is a piece of equipment, and you only get 1 per life.
15) Grenades are not considered equipment, and replenished by scavenger.
16) The M16 is in the game, and still a powerful weapon. (Or as Woody puts it, still the ****!)
17) The PSG1 sniper rifle is in the game.
18) UAV, airstrike and 3 types of helicopters are back as killstreaks. The Pave Low is confirmed as well, and has a feature unique to the game.
19) The SR-71 plane is also one of the killstreak rewards.
----------------------------------------------------------------------------------------------
News from May 28th, 2010 Apparently someone from Cubed3 interviewed the studio head of Treyarch, Mark Lamia, and got info that the wii version will have:
-online co-op
-very similar builds to 360/PS3 versions
-and Treyarch is trying to work with Nintendo to remove FCs and add Wii speak for the game.
links:http://gonintendo.com/viewstory.php?id=125153http://www.cubed3.com/preview/343However.. Nothing is 100% confirmed yet. I don't know how credible the Cubed3 preview interview is. So just hang on tight and don't get your hopes up...