*Whistles the M:UA theme*
Spider-Man: Web of Shadows will most likely be Activision's big holiday game. According to IGN.com, M:UA 2 WILL be out in 2009, later in Activision's fiscal year. The fiscal year of Activision goes through March 2009.
There's no official word on the platforms the game will be on (360, PS3, and Wii are pretty much a given though).
There's still no specific title given to the game (X-Men Legends II has "Rise of the Apocalypse.
According to 1UP.com, M:UA 2 will be based on the Civil War comics.
"In this story, superheroes throughout the Marvel universe are forced to register with S.H.I.E.L.D. if they want to keep fighting crime. The heroes end up splitting into two groups -- pro-registration, led by Iron Man, and anti-registration, headed by Captain America -- and the player will be able to choose which side they fight on in M:UA2."
According to Kotaku.com, the game will over 20 playable characters while will include the Hulk, Wolverine, Spider-Man, Venom, and the Human Torch. You will also be able to "fuse" the powers of two characters to create one character with "hybrid abilities".
Also, according to both 1UP.com and Kotaku.com, the platforms will be PS2, 360, PS3, Wii, DS, and PSP.
Personally, I hope it'll be on PC too, but I'll probably have a 360 or PS3 by then so it should be ok.
Sources:
http://xbox360.ign.com/articles/872/872831p1.html
http://www.1up.com/do/newsStory?cId=3168250
http://kotaku.com/5016629/marvel-ultimate-alliance-ii-details-platforms