I know some in the industry who don't need cutting edge hardware are looking at skipping updating to PCIe4 since PCIe5's development occurred concurrently and seemed mostly unhindered by the issues that delayed PCIe4, so the gap between product availability is apparently going to be far shorter than with any past revision, and any investment in hardware to fully take advantage of PCIe4 wouldn't be nearly as cost effective as PCIe5 if you don't need to do wide hardware changes in that ~18 months(Probably over 24 for consumer hardware though I think).