This week's edition of British satirical magazine "Private Eye" claims that the planned air date for the next season of Doctor Who is August 2014. This ties in with the Radio Times announcement that filming for the next season starts in autumn, so it's rather probable. If they're still casting a new Doctor right now, it's quite that the pre-filming process could take until then.
"Private Eye" has previously published some controversial reports on the show; the BBC went out of its way to deny claims that the 2012 series would consist only of four specials when the magazine reported as much in June 2011 (as it turned out, they were only off by two episodes, despite Steven Moffat's Twitter on the subject). Their report on Caroline Skinner's leaving has not been commented upon by any of the involved parties, understandably.