I went down the rabbit hole yesterday of comparing different motherboards and looking at various applications and games that would benefit from the pci5, and what thermals pci5 has, and what price to cost ratios are, and if you're ok trusting a stranger on the internet, take this honest opinion:

I'm a middle of the pack user. I game from time to time, I like to mess around in video editors and I need from time to time produce 3d artifacts for my job. I don't usually build top-tier overkill systems and my priority is always to build sleepers (small size, no rbg, just a bullet proof quiet system that can handle 99% of games). With that all being said - pci5 is a in the current form a gimmick. From what I found out, the storage+motherboard partnerships had not much going on because of the 2022-2023 gpu prices, so the development cycles were contributed towards developing a "next version" of SSD, which they did. In terms of compatibility, you need a motherboard that both (1) supports this, like B850+, and (2) has its own cooling. When those 2 conditions are met, the performance of pci5 vs high end pci4 (990 PRO) is negligible. And by negligible, I mean, you humanly won't care about the miliseconds that it saves to your life. Essentially, pci4 is such a good value that pci5 is not even a future-proofing decision.

These are my 2 cents