That would be overconfident. This prediction requires several burdensome additional details, including but not limited to:
The existence of the Holy Grail
The existence of Harry James Potter-Evans-Verres and his chaos legion, which ALSO implies additional burdensome details including that the laws of thermodynamics are wrong, there's a giant secret castle in Scotland where people learn magic, that giant squids live in shallow freshwater habitats, that faster-than-light travel is possible and that complete idiots could be in charge of insanely powerful magic for at least a thousand years without destroying the world.
Suzumiya Haruhi exists
Because of 3 and 2, there are two totally different systems of magic in the world.
Death Notes exist. (The probability of that given both 2 and 3 is not too bad, though.)
MoR Ginny will side with MoR Harry.
Ninjas currently exist.
Ninjas are planning to assassinate the President.
They're not just going to do that, but do it on February 13, as opposed to the 12th or 14th or some random day in March.
If Obama were assassinated, Sarah Palin would be electable.
Sarah Palin would actually try to become President under those circumstances.
To assign 99% probability to this requires some serious conjunction fallacy and something very wrong with your mind.
Alternative explanation: It's a satire of the (already ridiculously overconfident) prediction it was written in response to.
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.)