According to multiple sources for Polygon, Marvel vs Capcom 4 will be announced at Playstation Experience 2016. This makes sense as Capcom Cup 2016 Street Fighter V tournament will be held at the event.
Polygon also reports that Marvel Studios will allow characters who have become popular in recent films to be in the game. This includes Groot from Guardians of the Galaxy and Ant-Man along with the Avengers.
Keep in mind that Capcom nor Sony have confirmed this reports.