Brendan Moody wrote:
I doubt Jenna-Louise Coleman is going to be in the series past the anniversary special anyway-- as StCoop pointed out a while back, Clara's birthday is 11/23, which suggests her whole plotline is part of the anniversary build-up. They could be planning to keep her on after the mystery of her character is solved, of course. But even given all the gaps and schedule changes of the Moffat era, I'd be amazed if they were going to put of the start of post-anniversary filming that long.
If I had to guess, I'd say that filming on series 8 will begin in late June or early July, once filming on Sherlock
is done (and it's well into post) and roughly at the same time that season 7 finally finishes airing.
However, I freely admit that filming could begin much sooner than that. Heck, it could begin next month with the anniversary special filming coming where the third block would be.