The Threadripper 2990WX was already pushed to 5.4 GHz last week, but it looks like there is room for more overclocking when enough liquid nitrogen is used. Overclocker Ivan Cupa managed to get all 32 cores of the 2990WX model running at an outstanding 6 GHz, but there is no way of telling how much better it performs, as no benchmarks were provided.
https://www.notebookcheck.net/AMD-s-Threadripper-2990WX-overclocked-to-6-GHz-across-all-cores-with-LN2.323102.0.html