According to XFastest, which posted all of the images, existing LGA 1151 coolers will have no issue mounting to LGA 1200 motherboards. We'll have to wait and see if that is accurate across the board.
The site also says the Core i9-10900 is a 10-core/20-thread processor. That's consistent with previous leaks. Interestingly, past leaks also peg the part as having a 2.8GHz base clock, while the chip in the images above is stamped with "2.50GHz" on the integrated heatspreader (IHS). It's possible that the final silicon will be faster than the ES chip, though it's also possible that past leaks are wrong (or that things have changed).
Comet Lake-S represents another refinement to Intel's 14-nanometer node (14nm+++, if you're keeping count). Current plans are for it to top out at 10 cores/20-threads. The platform will will offer up to 30 PCH-H high-speed I/O lanes, up to 40 PCIe 3.0 lanes (16 CPU, up to 24 PCH), integrated USB 3.2 Gen 2x1 (10Gbps) support, Wi-Fi 6 support, and a few other odds and ends.
Intel has not yet announced a release date for its Comet Lake-S lineup, though rumor has it they will arrive in mid-March.