I was thinking about this last night... about the options they have.
I am not sure about how much of a solid timeframe the release date of the book gives, because I have seen those change a lot, very suddenly, especially with that particular publisher.
Then again, my thoughts are:
- The Alpha/F&F beta would have to start VERY soon for a release in June/July
- The Shattering was released on Oct 19th... 6-7 weeks before the Cata release. If the publishing date of the new one remains unchanged, we'd be looking at a release in early Sept.
- Would they even release a game in the summer? I was under the impression that thats an unpopular time of the year for game-releases (summer vacations, people being a bit less interested in gaming), but then again, I might be wrong
- Would it make sense to release it around the time summer-breaks end (Aug/Sep)?
- Would they really expect people to stick with 4.3 for a full year and actually put out MoP in December?

That approach, IMO, would be rather hardcore... it would be a rather reckless move, as to me, that would say "OK, some of you will stick with the game regardless of there being no content for a year, and all of those that will quit the game to check out other games because they are bored will surely come back for MoP"
That'd be a rather risky move IMO...there are several new games coming out in 2012, others (like SWTOR) might be developed further, offering more than they do right now, and I do think people will be bored by... I dunno, April?
With ICC, they did release the patch that opened it in Dec, a full year before Cata, but they did open ICC gradually, so the actual death of the LK didn't happen as soon as the death of DW.

I mean, 4.3 has been out for like 7 weeks, and to think of doing the three dungeons and those raids for another 10-11 months... I don't think Blizz expects that to work. I mean, if that was what will happen, people have enough time to gear all their alts all the way.

So I am quite puzzled by this, and if I was asked to bet, I would have no idea what month to put my money on...