Arthur Darvill has confirmed that he will be involved in the next series "in one way or another", implying that he won't be there full time.
Also, Steven Moffat has 'confirmed' that there will be a new companion next year BUT Moffat has been known to bluff, so take that as you will!
Oh, and a new companion! Yes, confirmed by @steven_moffat tonight! ;)
[Sauce]
