Why 6? Because we got 6 Xmen in MVC3/UMVC3 namely Storm, Magneto, Sentinel, Wolverine, X-23 and Phoenix. I know Deadpool is an xmen character too but we will not include him on this thread.
This is not about which xmen should benin the game but rather about which xmen do you think will be in Marvel vs Capcom: Infinite.