It's another Skylake-X refresh and will be supported by existing X299 motherboards.
The Core i9-10900X is a 10-core and 20-thread CPU is likely to become a lower tier in the CL-X CPU family. It is a successor to Core i9-9900X, which also had 10 cores and 3.5/4.4 GHz clock speeds (for base and turbo respectively).Based on the Geekbench score, VideoCardz notes there is minimal performance gain versus the 9900X. Overall, there's not much to get excited about, but Intel did promise that Cascade Lake-X would have a significantly better performance-per-dollar ration than Skylake-X.