Not necessarily. Timing is everything and having Bryan on board may have played a key factor in keeping this particular cast together. Keep in mind FOX is already rebooting Fantastic Four completely--all new cast, new director, new everything. And that franchise isn't even as old as this one. So it's certainly a strong possibility. The studio is clearly not against the concept of rebooting if it's necessary. The cannon logic can't be applied exclusively here because Xavier was f***ing vaporized by Dark Phoenix in X3. And he got a funeral. LOL And yet Patrick Stewart is signed on for Days Of Future Past soooo...never say never. Besides, it's been confirmed by a large number of on-line resources, including The Hollywood Reporter, that James Marsden was a focus of the studio at least as late as last December. So who knows? We didn't *see* him die in X3, unlike Charles Xavier.