Not necessarily, because you don’t know what happens in the future.
The park rate might very well rise even further long-term although it has started to decline by some percent short-term.
If changed park rates did have an effect on already parked NBT that would lead to
- an incentive to park only for the shortest time that is possible, because of the uncertain outcome
- higher parking rates to compensate for the uncertain outcome
That is right, but a floating park rate is kind of unexpected if the time frame of the parking is not variable after the parking has started.
A floating park rate would (likely) only be widely accepted, if parked NBT could be unparked at will and not only after a certain time has passed.