ASUS is announcing a workstation motherboard for the Z390 chipset, it is the WS Z390 Pro. It of course has support for 8th generation Core processors, but the big thing with this board is that it makes use of a PCI-Express 3.0 x48 bridge chip. This will convert 16 gen 3.0 lanes from the CPU to two 16 downstream slots, which are further split into four x8 slots. So the slot configuration would be x16/x16/NC/NC or x16/x8/x8/NC or x8/x8/x8/x8.
Besides the four x16 slots there is also a PCI-Express 3.0 x4 slot. This ATX board draws power from a 24-pin ATX, 8-pin EPS, and optional 6-pin PCIe power connection, and makes use of a 10-phase VRM. For storage you have two M.2-22110 slots, two U.2 ports, and six SATA 6GB/s ports. The M.2 slots are fully covered by large heatsinks.
There are two 1 GbE ports LAN ports on this board, one is powered by the Intel i219-LM, and the other by the Intel i210-AT. Rear I/O includes DisplayPort, HDMI, four USB 2.0 ports, six USB 3.1 gen 2 ports (1x Type-C, 5x type-A), dual Ethernet, and your audio connection. There is also a clear CMOS button on the rear I/O. The audio is powered by the Realtek ALC S1220A codec with audio-grade capacitors, a headphones amp, and ground-layer isolation.
No word yet on pricing, but expect this to be one of the more expensive Z390 boards.