We expect AMD Ryzen 2 processors to arrive during the first quarter of next year. Now, thanks to the confirmation provided by the PCI-SIG we can be quite certain that the new processors will be accompanied by the launch of an enhanced chipset: the AMD 'Promontory 400 Series'.
The PCI-SIG Integrators List details "the latest products that have successfully completed the rigorous testing procedures from PCI-SIG Compliance Workshops". If you click the link in the intro you will see that the 400 Series chipset from AMD is the latest product to have gone through this process. There are a number of fields in the table giving us further information.
Currently AMD and its partners are supplying 300 Series chipsets which include the B350, X370, X399 and so on. These existing available chipsets are capable of 5GT/s and feature up to eight PCIe 2.0 general purpose lanes. Thus a major advance of the 400 Series chipset will be the provision of PCIe 3.0 at 8GT/s, as highlighted by the PCI-SIG table. The new faster lanes could help facilitate AMD motherboards with more 32Gb/s M.2 slots, for example. We could go on to infer that the 400 Series chipsets don't include PCIe 4 and/or DDR5, or at least they haven't been tested in the PCI-SIG Compliance Workshop.
With Ryzen 2 processors on the way, existing Ryzen platform owners might want to upgrade. The new processors are expected to work on your current AMD AM4 300 Series motherboard with just, perhaps, a BIOS update required. Earlier this month the AM4 socket was confirmed to be ready for AMD Ryzen 2, and will remain current until at least 2020.