In this current generation, "world models" is basically a marketing term. You can research gaussian splatting, novel view synthesis, neural radiance fields (nerf), etc... I find Mr Nerf is good to follow: https://x.com/janusch_patas

There is another thing called world models that involves predicting the state of something after some action. But this is a very very limited area of research. My understanding of this is that there just isn't much data of action->reaction.

Same issue with gaussian splatting/nerf really, very little data (relative to text/images/videos) of text -> 3d splats. I'd guess what world labs are doing is text -> image -> splats, but of course it is just speculation.