Well that was surprising. I honestly didn't expect this to turn out to be true. Mostly because as Singer himself said, it's a very ambitions concept.
Obviously if they're setting the "present" in the 60's a lot of the details will change (probably meaning the dystopian future will be set in the X1-3 time-frame.)
The obvious question for me is which character should do the time travelling? I'm betting it's not Wolverine--though a little prologue cameo with him slicing up sentinels wouldn't be out of the question--and while I think it should be an already established character (from FC) I can't see it being either Magneto or Professor-X. Mystique would be an interesting choice I think. For one thing it'd help connect the dots between what we saw of her in FC and the ice cold psychotic killer we saw in X1-3.
The only other choices would be either Beast or Havok...or possibly Cyclops if we assume they're father and son rather than brothers as in the comics...on the other hand, perhaps Havok really is Scott's brother and he's already been sent back in time...? Nah. Too convoluted.
Mystique is still my favourite choice.