It is very likely that Intel will be forking their high-end desktop platform. Later this quarter you’ll see the new Z399 socket LGA2066 chipset later this quarter and then the X599 chipset that will power LGA3647 processors.
The X599 chipset is more than likely a response to AMD’s 24-core and 32-core Ryzen Threadripper processors that basically make Intel’s current “Basin Falls” X299 platform not competitive at all. X599 could be the C629 without many enterprise features and the addition of more client features. With this chipset Intel could become competitive again at the ~$1500 price range, where they plan to release 24, 26, and 28-core “Skylake-X” XCC chips.
Z399 could be for the lower 20 and 22-core chips for the LGA2066 socket. Current Skylake-X LCC and HCC would be compatible with the Z399 chipset and X299 boards could receive BIOS updates to support these new 20 and 22-core chips.
Since LGA2066 will not be “extreme” anymore the “X” in the chipset name has been replaced by “Z”. This should help consumers distinguish between Intel’s two HEDT platforms as well as set the platform apart from AMD’s X399 chipset.