It has been two films in the First Class timeline for young Charles Xavier and actor James McAvoy seems to have grown hair in the most recent film Days of Future Past instead of losing it. Of course there was that off-handed joke in X-Men: First Class where Hank McCoy says to Charles that Cerebro would work better if he shaved Charles head. But beyond that we have yet to see James McAvoy go bald leading him from simple telepath Charles Xavier to Professor X (Played by Patrick Stewart)
Well, while speaking with The Huffington Post the actor reveals that he doesn't have any specifics on the next X-film Apoclaypse but does reveal he will finally go bald:
"I'll be older for this one.[And] I think I'm losing my hair finally. And, yeah, that's kind of all I know." He continued, "I got an email from the [producer/writer Simon Kinberg] who informed me he was getting dead excited about stuff, but he didn't want to divulge anything for a couple of weeks, so I really don't know. It does seem fairly global, if we're talking apocalypse. Maybe it's just the character's name, but I think the nature of the film is going to be fairly apocalyptic."
X-Men: Apocalypse hits into theaters May 2016