Current Roster
Capcom Side: Ryu, Chun-Li, Morrigan, Felicia, Tron Bonne, Wesker Chris Redfield, Dante, trish, Amaterasu, Viewtiful Joe, Arthur and Spencer (Bionic Comando).
Marvel Side: Deadpool, Spider-Man, Captain America, Doctor Doom, Dormammu, Super-Skurll, X-23, Wolverine, Iron Man, Thor, Hulk, Modok, Magneto.
Current Stages
Asgard, the Helicarrier, underground Umbrella lab, Mega Man Legends stage (probably Kattelox Island) and Daily Bugle rooftop
interview with Ryota, about the character selection
http://www.gametrailers.com/video/final-roster-marvel-vs/703817
also
a MvC3 Comic-Con Build Write-Up thanx to Demon Dash