The immediate availability of the Rambus PCIe 5.0 controller could bring the first PCIe 5.0 commercial products sooner than previously estimated. This would indeed prove that PCie 4.0 was doomed for a short-lived interim. Features include backwards compatibility with versions 4.0, 3.0 and 2.0, plus 128 GB/s bandwidth in x16 configuration.
https://www.notebookcheck.net/Rambus-readies-PCIe-5-0-controller-for-licensing.442774.0.html