Although still not confirmed by Intel, it looks like the company's partners are ready to introduce the 500-series motherboards on the 11th of January 2021. A month or two after the introduction of these boards, Intel is expected to launch compatible Rocket Lake desktop processors as well.
https://www.notebookcheck.net/Intel-Z590-B560-H510-motherboards-rumored-to-launch-January-11-new-Rocket-Lake-desktop-processors-to-follow-later.509962.0.html