This literally just in from the BBC (yes, I have a smartphone nowadays):
Peter Capaldi to leave Doctor Who A sad day, as always, I think, although I'll be honest that I'm not entirely surprised given the impending Moffat-Chibnall changeover. The new guvnor, no doubt, will want to have the same chance to establish his vision of Who as Moffat got in 2010 (and hopefully it will be as great as the magisterial The Eleventh Hour).
I for one don't buy into the narrative about the past couple of seasons of NuWho losing their way; I actually think they contained some of the best stories since the revival in 2005, and Capaldi has always been a joy to follow both on screen and off. So it will be a sad day, but also I think an exciting one as Who does that thing it does and remoulds itself into a new era. I assume this means the 2017 Xmas special will also double as a regeneration story?
Anyway; thoughts, wild speculation, fancasting fantasies...? Please feel free to share all in the comments below!
EDIT:
More detail!