MSI has announced that their X470 and B450 motherboards will be supporting the AMD Ryzen 5000 processors. BIOSes for both platforms should be available to consumers starting January 2021.
Evaluations for their range of older motherboards, which includes their X470 and B450, MAX, or non-MAX products will be later be updated to have support for Zen 3 processors. At this time, however, the X370, B350, and A320 platforms won’t come with support for Ryzen 5000 unless AMD makes any official updates later.
A detailed BIOS release schedule will be announced after the BIOS code have been provided by AMD. Until then, you may find more updates for through their website.