if it's Half NAVI21, it wouldn't be too much to assume that it would have 64 MB of infinity cache. If they don't, well it would be hard to get a performance increase over the 5700xt if they only have a 192 bus unless they use much faster memory like GDDR6X. I find that unlikely.
As for memory, we are indeed into a position where we require way more ressource to increase significantly the graphics.
- Larger textures. That help on close-up but not much on object that are far away
- More texture : (like diffuse, normal, emission etc.).. this will improve graphic fidelity but it would need the engine to process it properly. Good ray tracing will require the usage of that.
- More unique objet. (each object will require unique set of texture and geometry), that may or may not have an impact on fidelity, but it may also have an impact on gameplay.
- More detailed object
- Larger environment with longer view distance
All that will require more memory. But the thing is right now, they scale memory on texture and things like grass because it can be easily scale down or up without too much impact. But at some point, a game will be made so the numbers of object, the details of each object and the size of the environment will be increased to match larger memory buffer.
Another thing is having a good sized memory buffer is you have more space to stream asset in and out and maybe limiting the impact of streaming on your FPS.
