OWC has launched a PCIe M.2 NVMe SSD card for the Mac Pro, and it looks pretty sweet:
Accelsior 4M2 NVMe SSD is OWC’s fastest SSD ever with over 6,000MB/s speed for large format video editing, VR/AR/MR environments, extreme gaming, and other high bandwidth needs. Available in capacities up to 8.0TB, Accelsior 4M2 is the ultimate performance drive for Mac Pro 2019, Mac Pro 2012 and 2010, and PC towers. It offers silent cooling via a finned heat sink cover and installation versatility with a half-length x8/x16 design.