Yes. It's a sufficiently weird feature of the kind of simulation I would join. An apocalypse seems fitting, and 12/21 is the most prominent date we had since Y2K, but it's more surreal and a nice numerological coincidence, so more likely. (See Theory of Narrative Causation.)
I'll state here, for the record, that at some point in the future (post-singularity?) I intent to implement Sburb, grab some friends, suppress their memories (and mine) and make a proper game of it. I made this decision back in 2011, when I first ran into Homestuck.
It is in the nature of my personality that I would probably be unable to resist using 2012 for the start date, not least since I have a bunch of nieces and nephews at the appropriate age to be players right now. :P
I have no idea how to assign a probability to this currently being the case, though. ^^;
Going through expiring predictions reminded me. Just as we did for 2010 and 2011, it's time for LessWrong to make its beliefs pay rent and give hostages to fortune in making predictions for events in 2012 and beyond.
Suggested topics include: Methods of Rationality updates (eg. "will there be any?"), economic benchmarks (price of gold has been an educational one for me this past year), medical advances (but be careful not to be too optimistic!), personal precommitments (signing up for cryonics?), being curmudgeonly about self-improvement, making daring predictions about the future of AGI, and so on.
As before, please be fairly specific. I intend to put most predictions on PredictionBook.com and it'd be nice if they weren't too hard to judge in the future.
(If you want advice on making good predictions, I've tried to write up a few useful heuristics I've learned. So far in the judging process, I've done pretty well this year, although I'm a little annoyed I got a Yemen prediction right but for the wrong reasons.)