After looking through a few sources, I've dug up who's in MvC3.
Marvel: Spider-Man, Hulk, Wolverine, Mr Fantastic, Captain America, Iron Man, War Machine (alternate Iron Man outfit) Elektra, Thor, X-23, Magneto, Dr Doom, Shuma-Gorath, Emma Frost, Deadpool, Super Skrull, Taskmaster, Juggernaut, She-Hulk
Capcom: Ryu, Mike Haggar, Frank West, Chuck (alternate Frank West outfit), Spencer (Bionic Commando), Dante, Chris, Morrigan, Arthur, Amaterasu , Albert Wesker, Zero, Chun-li, Viewtiful Joe, Trish, Tron Bonne (Megaman Legends), Hsien-Ko, Akuma, Felicia
So, yeah. No X or Volnutt/Trigger. X was announced to not be in the lineup, and I find it a bit off they would include a Megaman Legends/64/DASH stage, but not Megaman Volnutt/Trigger.
Marvel: Spider-Man, Hulk, Wolverine, Mr Fantastic, Captain America, Iron Man, War Machine (alternate Iron Man outfit) Elektra, Thor, X-23, Magneto, Dr Doom, Shuma-Gorath, Emma Frost, Deadpool, Super Skrull, Taskmaster, Juggernaut, She-Hulk
Capcom: Ryu, Mike Haggar, Frank West, Chuck (alternate Frank West outfit), Spencer (Bionic Commando), Dante, Chris, Morrigan, Arthur, Amaterasu , Albert Wesker, Zero, Chun-li, Viewtiful Joe, Trish, Tron Bonne (Megaman Legends), Hsien-Ko, Akuma, Felicia
So, yeah. No X or Volnutt/Trigger. X was announced to not be in the lineup, and I find it a bit off they would include a Megaman Legends/64/DASH stage, but not Megaman Volnutt/Trigger.