The Radio Times have confirmed that Jenna Coleman is staying with the show for the whole of Series 9.
During the Press Launch of "Last Christmas", Steven Moffat said:
"Jenna is in all of the next series, which we’re delighted to reveal. There was a certain amount of to-ing and fro-ing, wasn’t there Jenna?"Jenna Coleman confirmed that Peter Capaldi had played a big part in her decision to stay:
"I always think I’m quite good at winding up people on this but Jenna completely outplayed me when she said in an interview 'I’m not telling you if I’m staying or going because it’s just more exciting'. And it occurred to us all that we don’t start shooting until January so we could actually keep it a secret."
"It’s wonderful – a whole other series of stories with the Doctor. I couldn’t walk away with the story being unresolved, there’s so much more to do and I think [Clara and the Doctor] have finally just reached a point where they really understand each other."
"The arrival of the 12th Doctor has just dropped this bombshell and allowed the dynamic to totally, totally change so I think, just when Clara was feeling more comfortable in the relationship, it’s suddenly thrown something totally new up and I think the comeuppance of that and the story that we got to tell over the season has been thrilling."Peter Capaldi was happy with Jenna's decision too:
"I think Jenna’s been just fantastic and it’s been such a pleasure to work with her – and especially for me as the new person onto the show, she’s just been fantastic – and so I was so excited and delighted when she finally [agreed to stay]."I rather think most of us are happy with this - the character of Clara certainly seems to fit with 12 more than she did with 11.