A lot of stories suddenly doing the rounds that Matt Smith will be leaving the programme, regenerating at the end of the 2013 Christmas episode - all coming from the usual programme "insider". For all I know maybe he is. However, the story won't be filmed until after he has completed the movie he is due to make in the States after the Anniversary Special, and the Christmas story probably hasn't even been written yet - knowing the way that Mr Moffat works.
So not sure just what or who this "insider" might be.
All I'll say is: if it happens it happens, but for now this is just simply a rumour. Give it a few weeks and there will be a "time to rest the programme" scare as well no doubt.