I'm not sure I believe Navi is going to be a product exclusive to Sony. It is their next gpu architecture for the general consumer. It's their late 2019, 2020 roadmap, unless they plan on not releasing a new PC gpu until 2021.
I don't think anyone has suggested an exclusivity deal with Sony would prevent the release of PC products. But it's not hard to imagine a scenario where certain features are contractually exclusive and not available for use in other semi custom designs for a certain term.