@brendan: Short answer, no wait.
There's really not enough info around this stuff to make any informed decisions right now.
Gen 4 SSD for current games only perform a couple of percent better than NVME drives, and NVME drives are usually less than 10% better than normal SSDs. That's not to say games might one day be made to take advantage of faster SSDs, but that it isn't worth the money right now for unnoticeable performance differences. Who knows if the console SSDs will even translate to PC versions or if they'll be platform specific anyway. Gen 4 SSDs will only go down in price in the meantime and as long as you have a SATA or NVME SSD you'll get most of the benefit right now.
As for GPUs the (fastest card) RTX 3080 has essentially no difference at all between PCI 3 and 4, so you don't need to worry about that, I'd get a board that could handle both the GPU and SSDs running in PCI 4.0 just for longevities sake though. I think most x570 boards can do that, but you'll have to check the specs.
The limiting factors on you playing "next gen" will be your CPU and GPU, So I'd recommend using MSI Afterburner to look at your FPS, CPU and GPU usage and if the performance isn't to your liking using that to work out where you need to upgrade. There's not much point in having your games load really quick if your 1650S ends up running them at 30-40fps.
I'm guessing you're using a 4 core intel, so that'll probably need upgrading sooner or later anyway.
AMD are coming out with their Ryzen 5000 series CPUs in the next few months, so wait until then to see their performance and then get an 8 core 5000 series or 3700X and you should be set for the whole next gen, at least that's my plan with my 3700X.
As for case, as long as there's an mATX x570 board that lets you use your desired amount of gen 4 drives, without too many caveats you can stick with it, maybe buying a new one if you need room for a bigger GPU down the line or whatnot.
- Don't go all in on PCI 4.0 SSDs just for games, until it's shown that there's a requirement or noticeable difference
- Look at your performance and see whether you're happy with it / where to improve
- If you want to upgrade your PC wait a few months and get a 5000 series or 3000 series 8 core Ryzen , with an x570 board that gives you the option of getting gen 4 SSDs later on
- Invest your money into CPU and GPU upgrades before thinking about SSDs
- The rule with PC components is always, If you can wait, wait.