AMD claims in its latest financial report that the design of the Zen 2 platform has been finalized and the sampling for the Ryzen 2 desktop/mobility CPUs, as well as the EPYC Rome server cores will begin in late 2018, with worldwide availability scheduled for early 2019.
https://www.notebookcheck.net/AMD-s-7-nm-Zen-2-and-EPYC-Rome-CPUs-coming-in-late-2018.281504.0.html