Originally Posted by Marv
"Our" present would not be anything like the present of the original trilogy. You can't make an X-Men sequel with Jackman, Berry, Page, Paquin, Ashmore, Grammer & Foster if the characters they play don't even know each other in the new "present".
The new present is not the present at the end of X3 or Days of Future Past. That's why it makes a sequel starring that ensemble highly unlikely and nonsensical.
It depends how much is affected by changing the past. It needn't be a total rewrite, more than likely that key events happened differently or not at all. It doesn't erase everything.