On an official MSI account a customer service employee kind of has confirmed now that Rocket Lake processors and motherboards will get released in late March, kind of in line with the rumors. 

Earlier reports have indicated the new desktop processors to arrive roughly in the twelfth week of 2021, which starts on March 22. Intel itself reported last year that its Rocket Lake chips should be released in the first quarter of 2021. MSI also mentions that current LGA1200 motherboards will receive support for the new CPUs, these include H410, B460 and Z490 chipsets. Z490 motherboards will be the first to receive an update.

You may expect Intel to announce its desktop processors at CES, which will take place January 11-14. alongside Tiger Lake-H laptop processors that is.

MSI representative reports Intel Rocket Lake CPUs will be released in late March