Twitter user Kepler_L2 reports that AMD's upcoming RDNA3-based Navi 31 high-end GPUs appear to offer PCIe 5.0 X16 support according to the latest AMD's GFX11 architecture patches for Linux. Nvidia's Ada Lovelace next gen GPUs could get the same treatment, but rumor has it that these might launch at a later date.
https://www.notebookcheck.net/AMD-s-upcoming-Navi-31-high-end-GPUs-could-be-the-first-gaming-models-to-feature-PCIe-5-0-support.617362.0.html