The console prototype pictures appear to be legitimate, as the serial number on the back of the console was already claimed by a twitter user. Apart from the usual connectors, there also is a debug slot for gaming developers. As for the PCIe 4.0 SSD, it looks like Microsoft opted for the E19T controller that is just a bit faster than the current top PCIe 3.0 models.
https://www.notebookcheck.net/Alleged-Xbox-Series-X-front-back-pictures-and-PCIe-4-0-SSD-details-get-leaked.451042.0.html