"Doctor Who" In Two?

Stephen Moffat announced recently that he plans on splitting the next series of DW into two halves. Moffat said:

"Looking at the next series I thought what this show needs is a big event in the middle. I kept referring to a mid-season finale. So we are going to make it two series—seven episodes at Easter building to an earth-shattering climax, a cliffhanger we could never normally do because it would be too long before it came back. An enormous game-changing cliffhanger that will change everything. The wrong expression would be to say we are splitting it in two. We are making it two separate series."

So, what kind of game changer are they talking about? Something with River? Something about the silence falling, and the culprit behind it? Maybe River's homicide of the best man she ever knew? Knowing Moffat, it's probably something most people aren't thinking of, and I can't wait. Although it kind of sucks looking forward to next spring when there's only seven episodes.