Why should we see Xavier’s decision to step down after acknowledging all the mistakes he’d made as character growth when we know he’ll eventually be back to his usual routine.
As far as Professor X is concerned, the fact that he retired from working towards improving mutants’ lives flies in the face of him still teaching at the now-Jean Grey School for Gifted Youngsters in Days of Future Past.
Assuming that Wolverine still joins the X-Men in this revised timeline around the same time he did in the original timeline (i.e. circa 2000), then that means Xavier will be back to overseeing the team of mutant superheroes within 10 years or so.