I think you need to wake up and smell the coffee and stop arguing semantics. I think it's pretty clear where things are heading - Here's my prediction: When Sony announces their PS5 (which will probably happen after Scorpio releases), you'll hear that it'll also be compatible to your entire PS4 library (since it's - like the PS4Pro - going to be another hardware upgrade based on the same architecture). You'll also see games that are going to be announced that will not be exclusive only to the PS5, since it just hurts developers. A new console comes out and we go from a hardware platform that has 50 or so million installed units to, say, 5. So automatically, I would reach a MUCH smaller audience. So a lot of games will still be 'forward-compatible' - whether Sony forces that or not will be up to them.
I'm always a bit baffled that simply because the X360 / PS3 generation lasted for 8 years, people now think that's the norm. Hardware generations never lasted that long before. It's always been around 5 or so years, sometimes less.
On Microsofts side, I think they see a lot of power in giving players a huge variety of games - which is why the Xbox360 BC stuff now allows you to play hundreds of 360 games on your Xbox One. Being able to buy a new box and having access to a ton of older games mixed in with the new ones is a good thing. If I buy a new PC, I love looking at what my new hardware did to games I played before, it's great.
Looking forward, I very much doubt that any hardware manufacturer will make another super drastic cut like what we've seen before. That's partly the reason why they're all using an x86 base. It's just not necessary anymore and it hurts the entire industry every time with publishers not willing to spend high double-digit million USD on a next-gen game that has an installed base of 5 million units or so. We've already seen that hitting hard this gen and looking forward, hardware upgrades are going to be more gradual and happen more often. Sony dipped their feet into the water with the PS4Pro and Microsoft aims for a bigger splash with Scorpio, but the idea here is that the platform and the games available for those platforms are what's important, not the box itself. The box is just your access point and you'll be able to pick which box you buy based on your requirements.
You see people complaining all the time about lack of resolution or framerate for various games. The idea is to give people choice - if you're a hardcore gamer and you want your 60fps, you should be able to get a box that suits your needs. Right now console-manufacturers lose gamers to the PC because of that reason and in the future, you'll just get more choice.