Okay if a trilogy is done X4-X6, than there should be an overall idea of where things will go and how they connect. Its understandable that the Sentinels show up in X4, given the fact that it was teased in X3 and I'm sure the government doesn't know where Magneto is so they probably assume he's plotting something.
I want the franchise to go back to the basics of the first two films and not introduce people that don't serve a purpose to the plot. I don't know how people will react to Professor X acting as a parasite to a human host, this could possibly lose a lot of people so I don't know how they'll handle this because I sure as heck don't want Storm running the school.
I would like Cable coming from the future to warn the mutants of the impending doom.