It doesn't imply that the parking lots will stay there for 25 more years. It implies that until it is more valuable to construct something else on that land, the PV array would remain there for 25 more years. Whether or not parking is allowed under the array is entirely orthogonal.
You can't put a building there so most likely it would remain a parking lot. Sure in theory you could have a out-door market there but that is an extreme minority case.
There are simply not many other land uses that are compatible with installed installed solar panels.
And the chances of some other use is less likely if more is invested in the land.
