You should check the code of both world models (JEPA class for example) and compare to GPT. Many of the tricks stay the same, representation is still embeddings, there is a loss function, etc.
The exact architecture will change, but unless there's a new discovery in that area, we've cracked the text component already. We're hitting the limits of LLMs because of the intrinsic limits of text as a medium. But the way we work with text is pretty much settled, fundamentally.