Gigabyte and MSI are readying new motherboards designed only for Kabylake-X architecture.
Kabylake-X meets HEDT platform
The decision to put two architectures on the same socket generated some confusion among potential customers. Motherboard makers need to specifically tell customers that X299 motherboards do not support all features with Kabylake-X CPUs (for instance by covering DIMMs with stickers).
MSI and Gigabyte have brought a solution to this problem by introducing Kabylake-X only motherboards. Unlike most Skylake-X supported boards, these only have four DIMMs and slightly cheaper design.
The Gigabyte X299 AORUS GAMING is an ATX board with four DIMMs and three PCIe slots. It also has two M.2 connectors. With this motherboard, you can only use Intel Core i7-7740X or i5-7640X, but you will never have the option to upgrade to Skylake-X.
MSI’s X299M-A Pro is a micro-ATX motherboard with the same configuration as X299 AORUS, with the exception of missing PCIe 1x slots.