I doubt well ever see the second or third options being adopted as a pricing model by any of the console manufacturers as the only pricing model in the near future. Yes, Microsoft already offers Series X and S as part of their All Access program. But it is only an option and you can still buy it outright. Not to mention that this financing program has a very limited presence only in US and Canada, if I'm not mistaken.
Now to the first point and the whole concept of the Xbox portable. Why 500$? I think it is possible that if it happens it may be cheaper than 500$. Highly doubt anyone would sell a 500$ portable. Because as it stands, 500$ is a price tag for premium "4K 120 FPS" hardware. Can't go with the same price tag for a portable which will run games worse than so called "big" consoles. Don't really see such a portable being more expensive than 400$.
As for Xbox portable itself, it isn't happening for two reasons. First and the most important one - Microsoft said that they don't see themselves in the market to sell hardware. It isn't their goal or interest in gaming business. I swear they wouldn't have released Series X and S if they had a way to just move their 50m+ Xbox One user base to the cloud or PC. IMO, they make consoles right now more out of necessity, rather than their own will. If they could, they would have been out of hardware race already. Second - what would be the hardware for this console? Steam Deck is huge and it has just 1/3 of GPU power of Series S. Considering that Series S already came out and all modern games use it as a baseline, there is no option for Microsoft to introduce a hardware that is less powerful than that. Maybe in 5 years, when it would become possible to put Series S into portable? But it would be the time for the next iteration of hardware already.
The only thing that I can potentially see on this front fro Microsoft is some cheap always connected Android portable with xCloud app on it. Just like those Chinese Android handhelds. Anything more than that? Definitely not this gen.
