BBC will try to hold onto RTD as long as they can. When he does eventually walk away, they'll get on bended knee to beg and coerce Moffat to take over. If they can't get RTD or Moffat, they'll try Chibnall and if he turns them down, BBC will end the show.
Pretty much.
Shame.
But pretty much.
Maybe they could do a team a and team b approach, to avoid burn out, but I am not sure the egos could allow that to work.