When will the Twelfth Doctor's first adventure air?

There is some debate going around at the moment when the Twelfth Doctor will make his debut. The official word at the moment is that 11 will regenerate him at Christmas but there is a few conflicting articles going around. Here is a just a few options floating around at the moment.

Regeneration in 50th, 12's Debut story at Xmas
This would be nice as it would make the regeneration come as a surprise which hasn't been done for a while. (well, not the Doctors regeneration anyway) I do think that this is unlikely though as they seem amendment that Matt is in the Xmas special.

Regeneration early to midway through Xmas special
This is what I would quite like. The Doctor has nearly always (bar the TV Movie) regenerated at the end of the adventure but I think that it would be interesting to see the villain actually cause the regeneration and the new Doctor carry on and then save the day. It will also give us a bit more of a glimpse of the new Doctor. I know Steven Moffat has said that its going to be a traditional regeneration at the end of the episode but as we all know. Rule One - Moffat Lies.

Regeneration at the end of Xmas, 12's Debut Story in Autumn 2014
I think at the moment, this seems the most likely of the 3 I have listed. I think Moffat will want to give the whole special to Matt as his swansong. (and quite right too!) The thing with this though, is the fact we will have to wait 8 months after the regeneration to see 12 in action and this just seems like such a long time. I do hope that they consider doing a special at Easter or something so we can get to properly meet the Twelfth Doctor earlier than August.