Originally Posted by NanaT
There's the possibility that they may have Mystique already become the way she is in X1. They could explain her change in personality through the ten year gap. I completely doubt that though, but if that happened then there would be little reason for her to be a lead over Storm. As though you're right Mystique has a relationship with FC leads but Storm also has a relationship with the OT leads particularly Wolverine and Professor x.
I'm going off the assumption most the film will be in the 70's. Mystique is the obvious female lead there and will probably be important to the event that Prof X and crew need to stop. Anything can happen, I just don't see a role here for Storm except that of a team ensemble right now. Anything is possible at this point.