All Socket AM4 motherboards will support all Socket AM4 processors, which includes Zen 2 next year and Zen 3 in 2020. There will certainly be 500 series chipsets, but what new things they bring to the table are uncertain. PCIe 4.0 is a possibility. You will not, however, see 4 way Crossfire as some games don't even utilize two GPUs, and with DirectX 12, all multiple GPU coding is the responsibility of the game developer, and more than 2 GPUs is a waste. As for VRAM stacking, that and Zen 2 details should be revealed at CES next month.
