His career will outgrow the show. That's just how it is. It's a launch pad.
Even if he does leave after season 2 then I hope it's a hell of a send off and I wish him the best.
Dr Who has survived 60 years and one cancellation, it will survive this. Maybe it's paused for a few years, that's not a bad thing either. Break the doom spiral created by the Critical Drinker types and similar bias media.