Well it looks like we have our first X399 motherboard in the wild. It is the ASUS X399 ROG Zenith Extreme, which should be ASUS’s flagship X399 motherboard and this does appear to be the retail version as everything is in place and it does come with quite a lot of stuff!
The ASUS X399 ROG Zenith Extreme is of course based off AMD’s first HEDT platform with the TR4 socket. It is actually an E-ATX motherboard and includes features like the DIMM2 expansion card, LCD screen on the I/O shroud, four reinforced PCIe slots, PCIe Ethernet card, and WiFi. If you look close enough in one of the photos below you can see a ThreadRipper CPU as well.
Thanks Chiphell for the photos.