Thanks for the many replies everyone, especially those that gave their best sales guesses! :)
I agree that the restriction against games only for the "Pro" consoles from last-gen should be removed. At least for digital-only games, where it can be made very clear to the person that the game isn't compatible (on a base PS4 or Xbox One, it could actually pop up a warning if you tried to buy it on anything other than a "Pro" console).
As for it being worth it or not worth it, some of these "Pro" consoles are still in use with people who haven't been able to find a next-gen system yet. Others will presumably be passed on to others, so they have some life left IMO.
As for the argument that a mid-gen refresh should happen at least 4 years in, rather than 3, I agree. Microsoft did that with the One X and I think it made it a more interesting mid-gen console. I also think it will take longer before the current-gen consoles fall far enough behind PCs that a mid-gen refresh is necessary, since this gen the consoles aren't starting quite as far back as PCs as last-gen with its souped-up mobile CPUs (ugh).
As for it being technically non-feasible because even the Series S is more powerful than any of the last-gen "Pro" consoles, I understand that the Series S is more powerful. And worse, yet, DIFFERENT (compared to the One X and PS4 Pro, the Series S has a better CPU but not necessarily a better GPU). But, perhaps at a somewhat lower level of fidelity, it could be done reasonably well. Much closer to the Series S version than a base model from last gen could do at least.
To those who predict it won't happen, you're probably right. But it's nonetheless an interesting thought experiment, and something that would be cool to see happen. :)
To keep the old Pro consoles relevant in the upcoming next gens, assuming that's what you wanted, the best thing to do would likely be what MS has done when it comes to next gen (present) hardware. Assuming the tech keeps advancing like it has or even faster.
I was one of very few who thought replacing the XB1X with a new version, with new hardware as a low tier next gen console was a good idea for this very reason. Now you have to be careful about making sure the hardware isn't too weak but also that its not too expensive. The XBSS has the right ballpark price at $299, but is ever so slightly lacking in some hardware, though it's no doubt a better option than the XB1X overall.
Let the console gamers who care about lower prices play next gen games with next gen hardware, just let them play those games at reduced fidelity. This way they have a choice. If you want the best 4k and overall experience, you've gotta pay for the XBSX. If you don't and just want to play next gen games at reasonable fidelity for cheap, get the XBSS. With more recent impressive upscaling tech, this makes even more sense for the lower end SKU.
It makes sense, if that's what you're going for. If MS wasn't also planning to introduce cloud based gaming asap, a hard push to get people onto next gen hardware would be smart. If you compare the value of the XB1 at launch for $500, or even the XB1X at $500, vs the XBSS at launch for $300, then it's a no brainer to upgrade if you can get the cash. The only thing a company can really do to help those out who can't upgrade, is also what MS is doing with cross gen, but that hinders game progress. Cloud however may fix this problem in due time, perhaps.
It depends a lot on cloud gaming and how that goes. Game Pass as well. The better they do, cloud more so, the less reason to upgrade your hardware. Unless MS makes a change like Win 11 and forces you to get more recent hardware to use the service. Maybe, maybe not. Even then you'll have a cheaper option and I wouldn't doubt you'd eventually have the choice of a new Xcloud SKU for much cheaper than the XBSS.