From Event Hubs--
List of deconfirmed MvC3 characters and franchises
Marvel character deconfirmations
• Blade
• Daredevil
• Dr. Strange
• Emma Frost
• Fantastic Four
• Gambit (verified through uStream)
• Ghost Rider
• Kingpin
• Mojo
• Loki
• Punisher
• Silver Surfer (verified through uStream)
Capcom character deconfirmations
• Amingo
• Demitri
• Gene (from God Hand)
• Gill (from Street Fighter 3)
• Megaman X
• Nemesis
• Nero
• Phoenix Wright
• Ruby Heart
• Tyrant
• Vergil
Capcom franchise deconfirmations
Characters from these franchise will not be appearing in Marvel vs. Capcom 3.
• Breath of Fire
• Darkstalkers (no additional characters beyond Felicia and Morrigan)
• Monster Hunter
• Sengoku BASARA
Questionable deconfirmations
It's not official that these characters/franchises won't be making an appearance, but it's very unlikely most of them will.
• Akuma
• Black Panther
• Cyclops
• Dan
• Ken
• Man Thing
• PTX-40
• SonSon
• Squirrel Girl
• Wayne (Lost Planet)
• More Devil May Cry cast members
• Power Stone cast members
• Rival Schools cast members
• Three Wonders cast members
Official Cast Members for MvC3
For those of you keeping score at home, here's a list of currently announced cast members.
Capcom
• Amaterasu
• Arthur
• Chris Redfield
• Chun-Li
• Dante
• Felicia
• Morrigan
• Ryu
• Spencer
• Trish
• Tron Bonne
• Viewtiful Joe
• Wesker
Marvel
• Captain America
• Deadpool
• Doctor Doom
• Dormammu
• Hulk
• Ironman
• Magneto
• MODOK
• Spider-man
• Super-Skrull
• Thor
• Wolverine
• X-23