https://wccftech.com/msi-confirms-amd-ryzen-4000-zen-3-cpu-support-400-series-motherboards/

MSI in a recent MSI Insider briefing showed that its 400-series motherboards are planned to support AMD's upcoming 'Zen 3' microarchitecture. This MSI Insider video also showed that 300-series boards aren't expected to support the new microarchitecture. AMD has stated that they will be sticking with the AM4 socket but will be changing the chipset to ensure the maximum performance. Since AMD is changing the chipset, some chipsets may not offer support for older CPUs or older microarchitectures, even if the CPU does fit inside the socket of the motherboard.

In the MSI Insider presentation, there was a background slide which showcased which processors and which motherboards were compatible. Among the motherboards were A320, B350, X370, B450, X470, B550, and the X570 chipset-based products. This slide also showed how the X570 and B550 Motherboards were incompatible with the Athlon processors, and the 1st generation Ryzen processors while the newer B550 motherboards were also not compatible with the 2nd generation Ryzen processors in addition to the 1st generation and the Athlon processors.