Depending on Japanese media (inteview from COMPUTEX2018 oem partner) It is not Cascade Lake - X but Basin Falls Refresh.
Cascade Lake-X is aimed at next year's sales and they are.
Basin Falls is socket lga2066 x299 platform, this was run on their xeon purley platform with that lga3647 socket. There was no actual name given for the next x399, but I doubt it will have different socket from Basin Falls(Intel said them taking SkyLake X not Xeon Skylake SP, I really doubt you can drop 2066 pin Skylake X to lga3647 socket).
Purley platform should take Xeons from Cascade Lake-SP and SkyLake-SP families.