I'm a bit confused here are we saying that Radeon GPU's get more powerful over time? Or even weirder are we saying that Nvidia GPU's get weaker over time?
I think it's more about cutoff features in driver support.
Look at the The Witcher 3 for example, Nvidia pushed the hell out of Maxwell with this game, but when it came to Kepler, it wasn't given the same regard.
AMD is also guilty of this as well for example VSR the native downsampling functionality which AMD claimed was to be a feature of the R9 series due to a supposed hardware scaler was proven false when the R9 280 was stated to support this feature too, which was a nothing more then a rebranded HD 7950.
Someone did some snooping around and found out this VSR was nothing more than a driver level based downsampling and had nothing to do with a hardware scaler. AMD basically cut off the 7000 series of cards of this feature just to push people towards getting the R9 200 series.
Don't be surprised when R9 300 series comes out with some new feature, some of them will be missing from the driver support for the R9 200 series, just the same when Nvidia releases Pascal it will also push features that won't show up in the driver code for the Maxwell line.
Yes I agree it's misleading and I feel this is not the right way to go about pushing people to getting a newer card, if anything it pushes me away.
Cutting support and features at a driver level is the worst thing a GPU maker can do.