The trailer for Logan shows Charles Xavier to be still alive, even though enough time has passed for Wolverine to look much older than we’ve seen him in previous films.
This is very difficult to explain using either the timeline of X-Men: The Last Stand or X-Men: Days of Future Past.
In The Last Stand, Wolverine has pretty high healing factor while Charles Xavier is pretty old. Even if Wolverine's healing factor weans away gradually, I think it would make him live for at least 100 years more than other mutants. The same can be said of other timelines.
Can anyone please explain this?
Update: Regarding the similar question mentioned (How can Professor Xavier be alive?), this is not related to the events of X-Men 3 which caused the death of Xavier or the alternate timeline event(s) in X-Men: Days of Future Past which may or may not kill Xavier.
This is related to the pretty slow ageing of Professor Xavier as compared to Wolverine from a fixed year of observation.