I figure we're coming to the end of discrete generations sooner or later. We're 4 years into the PS5's lifespan and plenty of games still launch on PS4 because they don't need PS5 hardware, and PS5 will run them anyway.
It doesn't make sense to upgrade to a PS5 Pro if you've already got a base PS5, just as it doesn't make sense to buy a new smartphone every year. But I can see the idea being that whenever you feel due for an upgrade, you buy whatever the current model is.