Moffat has spoken to the authors of The Brilliant Book 2012 (Via Den Of Geek) about River Song and why he's made the choice to get Doctor Who aired in Autumn.
On River's future:
"That’s dependent on Alex Kingston”. He also confirmed that the Ponds are in Series 7.
On the move:
"The truth behind the delay next year is: why are we killing ourselves and risking compromising the show, in order to go out in the middle of summer? I’m sick of it. I’m sick of standing in the blazing sunshine, with a barebecue fork in my hand, knowing that Doctor Who is coming on any minute”.
And on the 50th Anniversary:
“Epic, huge, massive, indulgent... all your treats at once”. He adds that “I guarantee you it’s going to be the best year ever to be a Doctor Who fan. We’re going to be in production for longer than ever, just to do everything that we intend to do”.
See the full thing here: