At this point, there's really on incentive for hotels to drop reward prices for long-off reservations (like late 2020 or 2021). Assuming that Hilton operates their redemptions like the chain I used to work, hotels don't get paid for points until after the guest departs.
Dropping redemption rates now is not a smart move given the fact that demand might return to "normal" at some point prior to the date in question. It might make sense to drop cash rates if the hotel requires a deposit. The infusion of a small amount of cash might be helpful to some properties. But, points reservations have no immediate financial benefit to hotels.
What's important for hotels is their normal booking window. The booking window is the time-frame where the hotel gets most of their reservations. It will vary greatly depending upon location and type of hotel.
The booking window for property at a hub airport might be a day or less. A hotel in a downtown business district might be 10 to 20 days. For a resort on an island, the booking window might be 2 to 3 months because guests need to coordinate airline reservations to get there.
If the hotel is being smart, they won't even consider dropping points redemption rates until the beginning of their normal booking window.