We are only just now starting to see competition in PCIe 4.0 peripherals, and the benefits are really not that great over PCIe 3.0 for 95% of people. By the time the market is saturated, like we are now with PCIe 3.0 devices, PCIe 6.0 or 7.0 will be talked about as the latest and greatest. Focusing on one standard, and getting it right, will benefit the market a lot more than trying to implement the latest and greatest iteration. If AMD skips PCIe 5.0 till AM6 (or even AM7?), I don't think it will have much impact on their bottom line.
Look beyond peripherals. With pcie 5.0, you now need just 4 lanes to achieve same bandwidth as 16 lanes of pcie 3.0, you also need just 2 lanes on your nvme drive to ahcieve 4x pcie 4.0. now your cpu and chip has a 4x pcie 5.0 link thats equivalent to 8x pcie 4.0. it goes beyond PC.
That 4x link is a major bottleneck for the x570 chipset.