Depends entirely on Sony's design goals and performance targets. I reckon the PS6 will launch with RDNA 7 or later, by that time AMD should have a more fully fledged feature set with regards to ray tracing and upsampling hardware. Enough to catch up with its Nvidia counterpart? likely not.
Consoles don't generally have a straight GPU mapping to the PC side. Sony and Microsoft will customize things like the PS5's audio engine.
RDNA2 was a end of 2020 release just like the PS5, and that console uses a cross RDNA 1 and 2 solution. RDNA3 was a 2022 release, and RDNA4 will likely be a 2024 release. The PS6 is expected to be a 2028 release if it lasts the expected eight years. That points to it being a cross RDNA 5 and 6 solution, not 7 or later. We'll see what RDNA4 brings, and there will be roughly two more generations of improvements.
But that's assuming the PS5 sticks with an x86 AMD CPU/GPU solution. There's a good relationship right now, but the future could bring ARM, or even a switch to Nvidia or Intel graphics. If Nintendo is able to release a handheld hybrid that can hand PS5/XS games, while looking similar in graphics half way into the console generation, then who knows what the future will bring.
