Intuitively it seems like we could represent stable 3D positions and geometry that then passes through a separate shading stage.

Use a model to replace only the engine and game logic itself. Faster physics and rules than a physics engine. Much less human engineering needed to build a final product.

Add a final pass through an ML upscaler for photorealism or cartoon crispness.

I'd gamble 50-50 that this is an existential risk to Epic Games. I'd also gamble 50-50 that we see this in five years.

I can't think of any incumbent right now that is safe from disruption.