Re: Scratch, Scratch-scratch, Scraaaaatch
AMD have stated they will not support Zen 3 on anything other than X570/B550 (and the new 600 boards that are coming), this has already been confirmed in press releases from AMD and interviews with them.
Motherboards manufacturers, and many in the tech press, have stated the ROM size is a false, invalid excuse being made by AMD, people like MSI were just as surprised as everyone else when AMD said this, as they were still expecting until very recently, that Zen 3 support would still be coming to their B450 Max and other boards. Dropping support for older CPUs can easily free up enough space to add Zen 3, the issue then is the boards wouldn't support the older CPU.
Irrespective, motherboard manufactures can't add support for Zen 3 without AMD, so unless someone manages to get AMD to change their mind, then there will be Zen 3 on any boards other than the 500 or 600 boards.