Here is my take:
In 3-4 years, there will be a refresh of these machines. Buy the cheapest option available to play the exclusive games; after all, you'll be talking about their upgraded versions pretty soon anyways. There is no reason to spend 500+ on these machines unless you want bragging rights on how not to be frugal with money, and you are willing to spend that money again soon.
For me, I'll probably get a really cheap PS4 Pro/Xbox Elite soon after everyone upgrades to the PS5/X1SX just to see how well Sony/Microsoft were able to engineer the cooling/VR/Ray tracing on these machines. The first year these new consoles are going to be out, the consumers are really buying into future promises and testing out how well the hardware is made. I'll let my young gaming brothers and sisters deal with the beta testing, and I'll probably get it cheaper the next year on a Black Friday special.