Kagerow on 13 September 2016
Polaris is apparently last architecture to support GCN compatibility mode that supports PS4's original chipset, with HSA console design, linked CPU, and very high chance of picking HBM lines for GDDRs in next gen... While I doubt making it backward compatible is that difficult, it isn't out of possibility that Sony tries to get away with selling game twice by not even trying to implement backward compatibility and blame AMD for it.
If Microsoft and Nintendo both spectacularly fails instead of making returns, they will probably take that route.
