While I'm not quite sure what to believe regarding the status of the X-Men and Dr. Doom, I would say that people were a bit hasty to say that the new trailer confirmed they weren't in, since it clear they wanted to have one veteran and one newcomer for each side, and Iron Man, like it or not, is more popular than Wolverine at this point. Plus Iron Man works as a good counterpart to X. If anything, I'd question making Carol the counterpart to Ryu, but who knows sometimes why they pick who fights who in these trailers. Ryu was fighting Nova in UMvC3's opening cinematic, so I guess he's already gotten experience.
If there are two more characters revealed today though, I doubt they'll shed light on the whole Mutant thing, since its probably just going to be Captain America.