According to a report from ComputerBase, Biostar is joining Asus and MSI in supporting the new Ryzen 5000 (Zen 3) CPUs on its B450 and X470 motherboards. That's encouraging - because it isn't a strict requirement from AMD, it's up to motherboard makers to decide if they want to support the new chips on older platforms. Seeing a smaller player like Biostar participate bodes well for broader support for Zen 3 on 400-series motherboards; we expect that the remaining hold outs, Gigabyte and ASRock, will follow suit.
Biostar will begin adding support at the beginning of 2021 with a beta BIOS featuring AGESA code Combo-AM4 v2 188.8.131.52.
Luckily, Biostar's 400-series boards will keep all features intact in BIOS, meaning there will be no need to strip anything out to make way for Zen 3 support, like the cut-down GUIs we see with some motherboards.
However, if things go according to plan, backward compatibility with Zen 2 will be dropped once you upgrade to a Zen 3 supported BIOS, so beware, it is a one-way trip.
Ryzen 5000-series CPUs will drop on November 5, but again, you'll have to wait until January 2021 before you can run a Zen 3 CPU in your 400-series chipset motherboard.