Announcement here. But we're going to have to wait.
These new CPUs come accompanied by the new B550 chipset, which will ensure more cost-effective motherboards for those building on a budget. B550 will be the only mainstream modern chipset to support PCIe 4.0, so you can still benefit from extremely fast SSD speeds. The Ryzen 3 series is coming in May, but B550 motherboards will be a little behind, with models from the likes of ASRock, ASUS, Biostar, Colorful, GIGABYTE and MSI expected in June.