AMD will be supplying new Wraith Ripper coolers designed by Coolermaster that will allow the Threadripper 2990X to hit 4 GHz on all 32 cores on air. This was demonstrated during an AMD event recently held in Maranello, Italy. Getting all 32-cores to overclock to 4 GHz is a commendable feat, which implied much higher boosts on single and fewer cores.
https://www.notebookcheck.net/AMD-Ryzen-Threadripper-2990X-shown-to-hit-4-GHz-on-all-32-cores-on-air.320210.0.html