While resort fees are annoying, that's all they are. They are mainly (a) a way to look lower-prices on price-competitive searches and (b) a psychological trick to make people less price-sensitive when they book. I did notice as the resort fee on my favorite hotel has skyrocketed over the past few years from $12.99 to $27.99, their base rates seem to have gone down slightly. But I think a lot will depend on how things "open up." If they develop a test for people with antibodies and a significant number of people show it, meaning they are immune, travel should ramp up slowly and they will probably have to discount heavily. On the other hand, if we suddenly get a vaccine, I think there will be a torrent of pent-up demand, and they won't have to discount. Most people who have the money to travel aren't getting hurt that badly financially, the way that hourly workers are.
It's possible that some chains may open properties sequentially, rather than all at once, if they don't anticipate adequate demand.