Re: 800th Episode - 2014 Christmas Special (Rumour's/Poss. Spoilers)
I don't think Capaldi will leave after just one season; it wouldn't be very fannish, and nor would it really be fair to existing viewers. No real idea what his Doctor will be like, but I think he'll want to give younger viewers fond memories of a "Capaldi era" rather than just being an interim Doctor who essentially lasts just three months. I'm thinking three, maybe four seasons.
"Two things have always been true about human beings. One, the world is always getting better. Two, the people living at that time think it`s getting worse."