Re: What if... (poss spoilers)
Moffat has said this is going to be a "traditional regeneration story" so that likely means regeneration will occur at the end of the episode, like it has in seven out of the previous nine regeneration stories. Can't get much more traditional than that.
"Internet message boards aren't as funny today as they were ten years ago. I've stopped reading new posts." -The Simpsons 20th anniversary special.