Well firstly, there's no universal answer to that. It depends on how much you think the likelihood of them paying you back will increase if you help them compared with how much extra money you might spend in helping them. I personally think it makes sense to help GenCon. After all, if a bloke who owes you money is drowning in a river, it makes sound business sense to reach in and pull him out.
But secondly, there is a goodwill aspect. Gencon is a highly valuable asset for the gaming industry/hobby as a whole, and if they're seen to be kicking it when it's down, that doesn't make good sense from a marketting point of view.
Anyhow, not that it's relevent, but since I've booked a stand at GenCon (together with trans-Atlantic flights and a hotel room) I'm keeping my personal fingers well-crossed that this year's GenCon is a success.