Socket AM4 will be used through 2020, with all board partners supposed to be supporting all processors on all AM4 boards.
First, a question - Do you mean Ryzen Pro or Ryzen Plus?
Ryzen Pro is the commercial grade Ryzen, which means extended warranty and availability of parts, support for enterprise management tools, etc. These CPUs are otherwise the same as the consumer grade Ryzen.
Ryzen Plus is the Ryzen 2000 series that is set to launch next week. These will be compatible with existing motherboards (UEFI update may be required). There will be more detail at launch, but early indications are that there will be some additional features or performance that may only be accessed with the newer X470 chipset.