I don't know, a remarkably accurate full plot synopsis for Name of the Doctor leaked online nearly a month prior to that episode's airing, so there is precedent. Day of the Doctor was quite possibly the highest profile Doctor Who episode yet, so it makes sense BBC would go to extra lengths to try to keep things a secret. Also, maybe everyone's so burnt out trying to keep a lid on Day of the Doctor they just don't care if anything gets out about the Christmas special? Christmas specials usually get the highest ratings of the year and with this one getting added publicity by featuring the regeneration and riding on the coattails of the 50th, it's pretty much a guarantee that lots will watch it.
So, if the rumors are true, then the TARDIS was blown up at the end of series 5 by Spoiler: Culprit The Time Lords? I guess that would make some sense as to who could possible get access to and destroy a TARDIS...
If the spoilers are true, I'm kind of disappointed that Spoiler: rumors Moffat doesn't leave both "the Doctor is on his last life" and the "bringing back Gallifrey" storyline for Capaldi's run. Since we've already seen Capaldi in "The Day of the Doctor" we know that the Doctor won't die permanently in the Christmas special and since Eleven can remember those events he should know that, too. So, it's robbed of any tension it might have had. Brininging back Gallifrey would also have been suitable for a longer arc.
Apparently so, which would mean that Spoiler: rumours they kind of did delete the universe after all.
It would be an interesting contrast from Tennant if Smith's last words were something along the lines of "I'm ready" or "I suppose it's time".
Ummm... since our current Doctor lives in a fully rebooted universe, courtesy of that TARDIS-powered version of "The Big Bang", isn't he technically the current universe's first and only Doctor, and couldn't that alone give him a clean slate regeneration-wise?