"Castle Peak"will be based on the upcoming Zen 2 core, while this year's Threadripper gen 2 will feature a slightly improved 12 nm Zen+ core. The first Zen 3 cores are expected to arrive with the 2020 APUs.
https://www.notebookcheck.net/7-nm-Castle-Peak-Threadripper-desktop-CPU-coming-next-year-as-reavealed-in-leaked-AMD-roadmap.287686.0.html