I remain pretty convinced that Niitsuma held out vain hope for a while that one final patch / small DLC expansion for UMVC3 could possibly be made, and that's why there are certain teases in the game such as Mega Man's wanted poster being clean of any captured or dead text. They probably do have design docs for the other 8 characters that he wanted to do.
But at this point bad priorities screwed the pooch and it is probably a done deal. Really bad priorities. For example: given how popular SFIV and Marvel are in the tournament scene, it's pretty damn stupid that a patch for either game hasn't been made to enable stuff like select screen button check. But something like that would require a bit more financial investment, as it would require altering interface graphics and such. A pure balance patch for AE might happen because it is more practical within the meager resources being given the teams.
Sadly, Capcom suits seem as if they want to take advantage of the fact that there is an enthusiastic robust fan community for these games... but they don't want to invest in supporting said community very much. The game producers themselves want to support it, that is pretty clear at this point.