AMD will have next-gen CPUs and motherboards supporting the new DDR5 memory standard by 2022, but it will be Intel that is first-to-market with DDR5.
The upcoming Zen 4 micro architecture that AMD is aiming for a 2021 announcement and 2022 release, will pack support for both DDR5 and PCIe 5.0 support. AMD will be taking a big leap with Zen 4 as it will be using the 5nm node from TSMC, and then on top of that supporting both DDR5 and PCIe 5.0 stnadards.
PCIe 5.0 won't be so much for gamers as we're not really pushing the boundaries of things now with PCIe 4.0 (and most gamers are still on PCIe 3.0 -- it's only X570 chipsets from AMD and Radeon RX 5000 series cards that support PCIe 4.0). But servers, datacenters, and supercomputers will embrace PCIe 5.0 bandwidth with their arms wide, wide open.
Don't worry, DDR6 is already in development.