I'll go for 20 December.
I think most people have sussed it by now. Often the goat gets burned at some point, sometimes it survives until it's taken down in the new year. Yes it's illegal and no the organisers (officially at any rate) don't like the the "tradition" of burning it down.
For quite a few years there's been a sweepstake on the noticeboard - sometimes duplicated on FB now, where you can have a different guess. Yes people have guessed correctly quite a few times. the prize is some singed/un-singed straw - winner to arrange own travel expenses and collection.
Nobody has chosen survival yet, which is also an option of course.