I think the safety net would be the way contract law applies in a state of emergency - if the government says the event CAN'T happen, then there'd be no cancellation fee / forfeit of deposit, because the contract would be unenforceable.
EDIT: for WWE, I'd assume it's much more complicated, because they may be getting paid by Tampa to do the event, which would mean cancellation fees and maybe forfeiting the amount they were supposed to get paid. What I said above would apply for the indy companies that probably have pretty generic contracts ("I pay you X to rent a place, no cancellations more than X days before").