I see, thanks for the info. It does make sense since Gen 3 x8 x8 is sufficient for GPU and doesn't bottleneck.
But I am sure people will start comparing the Ryzen 8c16t (20 lanes) to 6900k 8c16t (40 lanes). Hope Ryzen will be more pocket friendly.
Ryzen definitely won't be a 40 lane CPU.
Looking at the back of the msi x370 board you can see the way it is hardwired(pic below) 16x on frist slot, 8x on the other 2 slot so most likely it will be 24 lane cpu.
Most likely config for the x370 board(enthusiast).
24 PCIe Gen 3 lanes (from the CPU).
16 PCIe Gen 3 lanes dedicated for graphics with support for up to 3-way CrossFireX(not sure) & 2-way SLI(x8/x8).
4 PCIe Gen 3 lanes dedicated for storage (NVMe, SATA & PCIe storage)
4 PCIe Gen 3 dedicated for LAN & USB3.1 Gen 2 ports.
8 PCIe Gen 2 lanes (from the chipset)
10 USB 3.1 Gen 1 ports (4 from the CPU and 6 from the chipset)
2 USB 3.1 Gen 2 ports
6 USB 2 ports.
6 SATA3 6Gb/s ports (2 from the CPU and 4 from the chipset)
But AMD has mentioned two full x16 (Gen3) lanes for GPUs. Board makers can add additional lanes through a PLX chip so we might see more features on later boards also we have not seen boards from asus yet.