Again, more fellow Whovians on fb than on lj, but it's a hassle to write long posts on fb, so I'll do this here.
I usually keep my early guesses to myself (mostly because I'm shy about guessing wrong), but to hell with that! I'm putting this all out here now, because I am absolutely intrigued with the hints about the coming plot, ooh yes...
So, the Question is the title. The question is.... will we actually learn the answer?
I think so. I think Moffat is just gutsy enough to do it. For one thing, I can think of no other reason why he would change the schedule of the series around so much. Instead of airing in spring and summer, season 7 will start in fall of 2012, then break like season 6 did, and end in 2013. The first episode of Doctor Who aired in 1963, placing the finale of next season in its 50th year.
I think Moffat wants to be able to say that this the show is which you do not learn the main character's name until 50 years after the program's beginning.
From what I've seen, his story-telling techniques are similar to mine. Along with his affinity for meaningful dates (formerly seen when he set the in-story date of the Tardis explosion to the actual date on which the episode was aired), he also reveals secrets the same way I love to, dragging them out with a mix of hints and red herrings, giving people time to guess and theorize all over the place before he finally gives us the answer.
He's also very bold. Test-the-boundaries bold. I won't even go into how much balls it took to do any of the River Song plotline. The Mary Sue accusations were flying after her introduction in season 4, and that was when we saw her die. To then reveal that she's his wife from the future, daughter of one of his sexiest companions, and a psychopathic assassin born and raised to kill him, who instead fell in love with him and broke the flow of time just to keep him alive a little while longer? Well, I said I wouldn't go into it...
The point is, I do believe that Moffat will answer the Question, whether he gives us an actual name or just a different title with some extra backstory. I read that he's drawing his ideas from the old series, so I did a little research...
and this is what I found. It wouldn't surprise me if Moffat has decided to finish what was started before the show was canceled. It could even be that he's uncertain about how long the new series will last and wants to get this out there as soon as he can, just to be safe. He was, after all, a fan of the show long before he was its head writer. Every fan wants to see a story's mystery solved.
However, The Other is not my only guess... Before I found the Cartmel Masterplan, I remembered the rumors going around earlier that we'd see a return of Omega. I think the only real piece of evidence for this theory is the badge worn by the Clerics...
Notice it here on River's arm, an omega symbol with... is that an 11 written through it?
The Question will be asked at the fall of the Eleventh, or so it was said in the latest episode.
Of course, Omega made a couple appearances in the old series, as an enemy of the Doctor's, but we've seen other such enemies turn out to be twisted versions of the Doctor himself - the Valyard and the Dream Lord. It's not impossible, especially given that the Cartmel Masterplan was also going to place him as a partner of Rassilon's.
Here's the wiki on him.
Certain details from the novels make this more likely, but the novels are often considered alternate universes. It depends on Moffat...
So, Omega or the Other are both possibilities. What I'm really wondering is why the Silence cares. They believe he must be silenced before he can answer the Question, so what kind of power, exactly, would that answer bestow to those who discovered it? Or, what kind of doom? They say his future is much more devastating than his past, so what will the Doctor become that could be worse than the man who destroyed his own species?
There is also the Valyard, that wicked version of the Doctor I mentioned once already. In the old episodes in which he appears, it's said he comes from a time during or around the Doctor's 12th regeneration. Which would be, you know, after the fall of the eleventh....
And that's all I've got right now.