Originally Posted by BobJM
Or if Xavier is using Cerebro to induce time travel,
Bingo! As long as Cerebro exist in both points in time. I'm sure the mansion is destroyed by Sentinels in the future but if they have a basic version that can transport Kitty or someone else's mind back in time and downloaded through the past Cerebro.
It will probably be someone that appears only to Xavier through the astral plane like a ghost.