From a promoters standpoint, seems like you could go almost down to the wire before a voluntary cancel. Not sure what deposits, insurance, etc costs that would forfeit.

The main issue would seem to be how much ill will with attendees that would generate. I would guess anything less then a weeks cancellation notice would be a negative.

So wait it out?

No reason to cancel early, unless postponing.

Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.