Casting rumors make the rounds every so often, so I don’t put a lot of stock in them. The current rumor is that Jenna Coleman (Clara Oswald) will be leaving the case of Doctor Who at Christmas. My understanding is that it was The Mirror that broke the story, but I’m not putting in much stock of it being true.
However, the idea has been gaining momentum, for several reasons. Clara’s main draw was that she was “The Impossible Girl”. With that story arc complete, she’s served her purpose. How much more can be done with her without it feeling as if she’s dragging on. Companion roles typically aren’t as long as a Doctor’s role. There are also rumors swirling around that Peter Capaldi may only do one season or two seasons. If Coleman were to leave at Christmas, the Doctor would be without his usual companion (which is the norm) and then could get a new one before regenerating. The other thing that’s been making people talk is Coleman’s Twitter account. She’s been a little active on there lately, and Karen Gillan (Amy Pond) became active on Twitter right around the time that she left Doctor Who.
Draw your own conclusions. For me, it’s more of a wait and see approach. Opinions?