IGN: What is the balance between the first classers and the original trilogy actors in Days of Future Past?
Singer: The movie takes place at different times. It deals with, I don't want to say time travel, but time displacement. A form of time travel which is steeped more in the X-Men [mythos].
So now that we have Blink's portals involved, I'm seeing displacement as meaning something else. Maybe this will be more like TOS' Mirror, Mirror(without the goatees) since Singer is a Trek nerd.
We know the two Charles don't share scenes, but maybe Magneto is the one "displaced" so a future X-man can warn past Charles and in doing so, Young Magneto meets his future self.