In Issue 465 of Doctor Who Magazine, Steven Moffat may have dropped a few hints about this year’s Doctor Who Christmas special.
Asked about how the TARDIS exploded back in Series 5, he said:
“Oh, never mind the TARDIS blowing up, what about the endless, bitter war Kovarian was on about? And what’s Trenzalore? And the oldest question in the universe? And what exactly do they mean, silence will fall? Anyway, I’m off to a read-through…”
The read-through was for this year’s Christmas special, and took place on Wednesday, 4th September 2013.