The Zen3 architecture underpins AMD's Ryzen Threadripper PRO 5000 series CPUs. CPUs with as many as 64 cores are available for high-end workstations. 

This anticipated March 8th launch is just for OEMs and system integrators, it should be noted. Later this year, the DIY market is expected to begin. Processors in the Ryzen Threadripper PRO 5000 series for workstations are the first Threadripper devices based on the "Zen 3" microarchitecture and include 8-channel DDR4 memory and up to 128 PCI-Express Gen4 lanes for workstation connection. They are designed for Socket sWRX8 motherboards and are not available in the retail channel. At the moment, it is unknown if these chips utilize the newer "Zen 3" CCD with 3D Vertical Cache or the more traditional "Zen 3" CCD with 32 MB planar L3 cache.

The EPYC "Milan-X" data-center CPUs from AMD will also soon be available for purchase. These are the Zen3 CPUs with 3D V-Cache added to them and provide 100 MB of total cache per CCD and 800 MB of total cache for the 64-core/128-thread variant.. Reports indicate Milan-X will be launched on March 21st. The same architecture with 3D V-Cache will be available to customers on March 14 or March 21 for the Ryzen 7 5800X3D. 

Specifications of the new AMD Epyc (Milan) processors now can be placed into an overview, the TDP of the new chips appears to stretch to 280W for the fastest clocked flagship model with 64 cores and 128 threads, as can be decrypted using the diagram below, a slide posted by ExecutableFix on Twitter.  Below you can see the nomenclature and table with alleged processors and specs.

AMD Threadripper PRO 5000 and EPYC Milan-X Likely to become available in March