We could soon see AMD launch its 400-series chipset close to Ryzen 2000's launch early next year. Existing 300-series boards will, however, continue to be compatible with the next generation Ryzen CPUs.
https://www.notebookcheck.net/AMD-Promontory-400-series-chipset-with-support-for-next-gen-Ryzen-coming-soon.274276.0.html
With a well endowed 64 lane TR (x399), an 8 lane chipset instead of current 4 lane sounds good.