Capcom don't need a MVC3...They have enough characters already.

We have established the fact that there will never be another marvel game in Capcom because they lost the rights to the franchise, but Capcom doesn't need marvel characters to make another 2D fighting hit game. Just think of all the characters that Capcom has at it disposal. The characters from the Street Fighter series alone is enough (SF2, SFalpha, SF3, SF EX)...not to mention Darkstalkers, Final Fight, Mega Man, Powerstone, RedEarth, Rival Schools, and SO MANY MORE.

What about SF v Darkskalkers v Rival School??
Games like Rivals Schools, Darkstalkers and Final Fight has a complete Roster of characters that Capcom and create into a good 2D fighting game. Street Fighter alone has enough to do on it own if you count all the character.

Here is just an example of "some" the characters that can be used in an "All-Star" game:

Street Fighter (entire series)
Ryu, Ken, Chun Li, Vega, Akuma, M.Bison, Guile, Charlie, Juni/Juli, Karin, Sagat, Balrog, Cammy, DJ, Fei Long, E. Honda, Sakura, Alex, Elena, Gill, Twelve, Remi, Sean, Ibuki, Mokoto, Yun/Yang, Q, Ace, CrackerJack, Doctrine Dark, Shadowgiest, Sharon, Skullomania, Garuda.

Darkstalkers
Demitri, Morrigan, Lilith, Felecia, Anakaris, Lord Raptor, Pyron, Bulletta/BBHood, QBee, Jedah, Donovan.

I could fill up the post with characters from a lot of other games, but you get the point. I just think that Capcom could create a new game using only the charcters that they already have.