So yeah, rumor has it that the last remain Capcom characters to be revealed for Marvel Vs. Capcom 3 are Hsien-Ko (Darkstalkers), Akuma (Street Fighter) and Haggar (Final Fight). The remaining Marvel characters are Phoenix (X-Men), Sentinel (X-Men), Taskmaster (Avengers... sort of), and the final boss; Galactus (Fantastic Four). There are a bunch of other notes to go along with these reveals; Take you for a ride supposedly plays during the credits, Phoenix Wright, Mega Man, Venom, and Frank West were once planned for the game but didn't make the final cut, there will be more DLC characters, that sort of stuff.
My guess is that some of it is legit (like Haggar) and other parts aren't (no Frank West? Really?). We'll know for ourselves soon enough, as MvC3 is set to drop early next year.