Marvel Ultimate Alliance 1/2 was relisted on xbox live, as is other games like Deadpool, Spiderman Shattered dimensions have also resurfaced. In the case of Ultimate Alliance, there are several xmen and Fantastic Four characters in it, so I'd think at this point the main issue is Capcom not being able ( or wanting) to cough up licensing fees again.
If Sony wanted to score a coup( seeing as they bankrolled SFV), maybe they'd consider funding exclusive rights to distributing UMvC3 on PSN, or since remastering is a thing this gen, working with Capcom on funding a ps4 remaster. And, if there's any beef with respects to the Xmen characters in the game, replace them with any number of characters from recent MCU movies. There's no shortage of formally obscure characters who are getting their moment in the sun now. Heck, Rocket Raccon is in the game, and he's far more known now after the GOTG film. Throw in Star-Lord, Groot, and give us Winter Soldier, Loki and Ant-Man while they're at it.
Or, just give us MvC4.