At thw recent screening of this years Christmas Special The Doctor, The Widow and the Wardrobe, Show runner Steven Moffat announced that the Pond's would be leaving sometime in Series 7.
"The final days of the Ponds are coming," Moffat said. "I'm not telling you when or how, but that story is going to come to a heartbreaking end."
He also said that the Doctor would meet "a new friend".
Matt Smith had this to say:
"We had the most incredible journey. We took over the show and we've really had to hold hands and help each other through it. So it's very disappointing, but one has to remember that this show is about change and regeneration, and that's what galvanizes it and pushes it forwards."