https://wccftech.com/amd-adds-support-zen-3-processors-to-x470-and-b450-motherboards/

AMD just provided an update on Zen 3 compatibility for X470/B450 motherboards from its official reddit account. It looks like the company has listened to the community and enable support on the older motherboards for its next-generation Zen 3 based Ryzen 4000 CPU family. They stated that they have reviewed the feedback provided by the AMD community and decided to 'change course'. This is an extremely admirable response from the company as it shows they are open to feedback. It's worth noting that the upgrade process will not be an easy one considering the technical limitation and safety design standards that AMD has to follow.

AMD had previously stated that they would support the AM4 socket till 2020 and while the company could theoretically have wiggled out of the promise they have decided to give the community what it wants. AMD's Zen 3 based CPUs, the Vermeer family, is expected to launch this September and will be based on the 7nm Zen 3 architecture. The reason why they hadn't been supported in the first place is because there is only a limited amount of space available on motherboard ROMs for support of CPU microcode.