If Sigma gets in a fighting game it might not be TvC2 (assuming we even get that). Note that every character in TvC aside from Doronjo is a hero, similar to how they pulled MvC1 off.. I mean, they could pull a MvC2 and just start adding people regardless of affiliation, but I'd think that hero characters would more likely see game-time first. Assuming that TvC2 would keep all of the characters from the prequel and add new heroes, they'd probably go for a series that hasn't been represented yet. Model X/ZX/A's a possibility, as would be a BN/SF character.