Internal Asus documents point to at least two AMD X590 boards in development. This was confirmed by an Asus source to Videocardz. Not much is known about the X590 at the moment apart from the fact that AMD could be aligning its launch to that of the 16C/32T Ryzen 9 3950X in September. Also on the anvil is an AMD X599 Zenith II Extreme for the upcoming Threadripper 3000 series.
https://www.notebookcheck.net/Asus-working-on-AMD-X590-and-X599-motherboards-to-cater-to-the-Ryzen-9-3950X-and-Threadripper-3000-series.428483.0.html