The only protections are those protected in the civil rights act of 64. “Employment at will” literally means you can be fired for any reason other than protected reasons (sex, age, race, religion, origin, sexual orientation now, and a few others probably).

So I would doubt it, unless the Florida governor put out an executive order stating that companies can’t fire employees who are scared to return to work.

And even then, if employees hold out and don’t get fired, wouldn’t Disney be able to just hire temporary employees? Given the record unemployment level I’m sure there are plenty of people who would agree to even a temporary job at Disney