The memory speed has been increased to DDR4-2933 for 1 DIMM per channel and DDR4-2666 for 2 DIMMs per channel, and the maximum system capacity has been doubled to 256GB. There number of PCI Express lanes has seen a small increase too, from 44 lanes to 48 lanes, but these are still PCI Express 3.0.
Another point to note is that Intel has stopped this stack at the 10 core and no lower. This means that there will be no cross over between Intel's consumer processor stack and the HEDT stack, with users needing to spend just a little bit more from the Core i9-9900K/KF to reach up to the Core i9-10900X. It will be interesting to see where Intel's Core i9-9900KS fits in, although that still only has dual channel memory and 16 PCIe 3.0 lanes.
More details at AnandTech. The launch date is October 7th but the actual availability date is sometime in November. AMD's third-generation Threadripper is also expected next month.