Everything that follows is unconfirmed, but the general information sits very well with well-sourced rumours that have been criss-crossing behind the scenes for months now. You may also consider it a spoiler, so turn back now if you wish to maintain your beautifully, pale purity. Congratulations on that, by the way. Don't meet many unicorns around here.
So, this new rumour hangs on the following tweet.
@DWSpoilers Sylvester McCoy just said he knows who's playing the new Master 'he'll be very scary'…
— Brett D (@BrettD262) March 8, 2014
Now, if that's true, and if Brett's further comments can also be taken as accurate, Sylvester McCoy has been told not to share his knowledge of who it is that has the role. This implies that McCoy's source is official.
And what this would mean is that The Master will be back, and in the upcoming series.
I've heard people suggest that either one of Charles Dance, Michael Smiley or sometime Eastender Steve John Shepherd already has the role. I wonder how much is rooted in online gossip, however, as searching each of those names turns up some blog post or newspaper report.
Still, Smiley in particular has proven how scary he can be when working at full bore and would be an exciting new take on the character, but one might also suspect that his casting in Ben Wheatley's episodes suggests a smaller part, not something bigger, series-spanning and Steven Moffat-sourced.
We'll see, though, and if they are going to film scenes with the mystery actor being all Master-ly in public, I expect we'll get an announcement from Auntie Beeb just ahead of time.