Stuff using PCI Express 5.0 is still coming out, while the PCI Express 6.0 spec is already finalized and will show up in PC parts eventually. But have you thought about what's next after it?

The Renesas PCIe 4.0 Dual Mode Link Controller IP is compliant with the "PCI Express (PCIe) 4.0 Base Specification". This IP supports the major functions required as PCIe link IP for embedded systems.