He tweeted earlier this evening, confirming the news, his later tweets can also be seen below in order:
There will not be a full series of Dr Who in 2012! BBC confirms that BBC One Controller said this earlier today. #drwho
BBC also says Danny Cohen’s remark that short series was because Steven Moffat needed time to write Sherlock was meant to be light hearted.
The BBC has, of course, commissioned 14 new episodes of Dr Who (hurrah) so looks like some will go in 2012 and remainder in 2013.
The news was originally revealed by @WayneAClarke who was at a conferrence where Danny Cohen was speaking.
Thanks to Combom.