This is an interesting summary of the rumours and then great speculation as to how everything might work. I still wish that David was staying on one more season, just to work with Moffat, but at the same time, he has good reasons for leaving. I'm reminded of Pertwee talking about how various people were leaving, including Barry Letts and Katy Manning, and it just seemed to him like a good time to leave as well, sort of like an era coming to a close.