Let me start by saying that as of right now, the Doctor Who showrunner job is not officially available and that Steven Moffat is expected to be back at the helm for season 10… which isn't expected to air in 2016 because of Moffat's commitment to working on the next season of Sherlock.
But there has been rumors of a change which may be fueled by the on-line "hatred" that the series showrunners have to deal with and the delays cause by Moffat's other successful series.
The rumors have gotten so rampant that Being Human series creator Toby Whitehouse had to come out and deny that he is up for the job. He has said it would be tempting, but he has had no conversation with anyone at the BBC about it.
The latest rumor has the Sherlock co-creator Mark Gatiss stepping in as showrunner and saying that it will be announced this Friday. Not sure how much stock to put into that though as Gatiss would be just as busy with Sherlock as Moffat… maybe even more so since he plays Mycroft Holmes as well.
At this point, all of the replacement talk could just be negative backlash from the internet and wishful thinking by the anti-Moffats. But that's a whole lot of smoke not to be attached to some kind of fire.
Or maybe it's just special effects dry ice?