See Film School Rejects new video interview with Steven Moffat HERE. Below is a quote from the interview of Steven talking about this years series finale.
“This time round it’s pretty big, but then it’s kind of intimate as well, it just depends on what’s the most dramatic thing to do. It’s always dramatic if you’re threatening the entire Universe, but then it’s equally dramatic if you threaten just one person. It has to be huge for the characters. What I’ve got in mind for next year’s finale is a smaller story, but it’s something that has a huge impact on the Doctor himself.”