So there is a demo out now showing some story and a handful of fights. You do get to play as X. He seems interesting, definitely not a clone of Mega Man from the old MvCs. His charge shot is a fireball motion, and he has followups for it, offensive and defensive. All his specials are projectiles: Boomerang Cutter, Sonic Slicer, Frost Shield, and Rising Fire. When he has his armor, his charge shot super can become the X2 double charge shot. And he uses Ultimate Armor in his level 3.
Zero will also be playable down the line. So I'm super dead wrong on my prediction. 3 Mega Man characters, all from the X series. Would've liked some variety there, but assuming the leaked roster holds up, disappointment is the name of the game. Although to be honest, I don't mind the gameplay.