After facing a major backlash from AMD fans, team red has announced that it will in fact provide support for its Zen 3 Ryzen 4000 CPUs on x470 and B450 motherboards via a BIOS update. It will require a small workaround, and will permanently disable those boards from being able to support older-generation Ryzen CPUs, but that still means that existing 400-series motherboard owners will have an upgrade path to Zen 3 CPUs.
AMD has been using its AM4 socket since the first-generation of Ryzen processors was released in 2017 and promised that all motherboards that supported the socket would be able to support AM4 CPUS through 2020. While that has technically been correct with Ryzen 4000 APUs released in early 2020 still supported by first, second, and third-generation motherboards, AMD soon after announced that next-generation Ryzen 4000 desktop CPUs would not be supported by even second-generation 400-series motherboards.
To many fans, this was a reneging of promises made by AMD about upgrade path potential over the years and left many facing a more costly upgrade when next they want to buy a CPU. AMD since explained that the reason for this lack of upgradeability was a technical problem, as adding the capabilities would mean locking out such boards to older processors.
But after much fan demand and consternation, AMD has listened to the complaints and has pledged to release a BIOS update to its board partners to make x470 and B450 motherboards compatible with Zen 3 CPUs.
There are some caveats, however. AMD motherboards flashed with the Zen 3-compatible BIOS will not be able to flash back. They will also lose support for older CPUs, so will only be compatible with Zen 3 chips moving forward.