He's been doing some interviews and stuff for this, and in it he indicates the window for him to sign on to Series 8 has passed, so he won't be doing an episode. He said before he was trying to find time for it. He pretty much says he'll be back for 9, though.
Regarding Gatiss, I do think he has a weak suite of episodes (his best only sits near RTD or Moffat's batting average, I think) but he's also the one of the people on the series who'd likely tick every single box the BBC will be glancing at AND would get the nod from Moffat and/or RTD if asked.
The boxes I'm talking about are:
- Has ran successful shows both at the BBC and elsewhere prior
- Has successfully produced (British, small-scale) movies
- Accomplished/Award Winning Writer
- Incredibly well-versed in Doctor Who lore
- Wrote four NSA novels and was involved in other Who pulse-keeping activities while the show was off-air
This is basically the same list of qualities RTD and Moffat both fit, and none of the newer people like Whithouse quite fit all the criteria, and thus would, on paper, be a greater risk. I think in particular the 'old boys club' sense of those people who did the Virgin novels and things like that burns particualrly strongly, and I think whoever takes over next is likely to be from that same pool. Sherman never returned after 'Dalek' - he never got the timing right despite being invited back by RTD, and allegedly he and Moffat don't get on - and others have dropped off similarly, leaving Gatiss. His episodes have been weak, but that said I think Gatiss could be a GREAT Doctor Who showrunner, but if he took on the role I'd like him to write less than RTD & Moffat did per series.
My worry with him is where his personal interests sit - if you look at his episodes, you've got: Victorian Britain, 1950s, World War 2, 2011, 1980s, Victorian Britain. Even his NSA novels are similar - with no budget or FX shots to worry about in novel form and only his imagination the limit, three of the four novels are set in Britain, all in the recent past and one in WW2. He has a very particular interest in Earth and the past, especially in a slightly jingoistic-feeling view of Britain. If he is to take over, I'd like him to do something well out of his comfort zone in Series 8, which he's already said he's doing stuff for.