Originally Posted by BMM
Stewart's involvement is the one I'm most curious about, at this point. How does his Xavier fit into all of this?
Well Xavier could be from the alternate Days Of Future Past timeline.
If the event that happens in the 1960s creates two different timelines. The first timeline being the original one which is the original X-Men Trilogy and the second timeline which is the Days Of Future Past timeline.
In the Days Of Future Past timeline none of the events from the Singer and Ratner X-Men movies took place so characters that died, depowered, ect may still be alive and vice versas.
With Xavier we might get a Wolverine and The X-Men or X3 type thing where he transfers his consciousness or someone elses into another body.