depends what you mean by 3d. jpeg-xl does let you add arbitrary channels, so you could add a depth channel, but it's not going to do a good job for full 3d (e.g. light field/point cloud).

one place I think jxl will really shine is PBR and game textures. for cases like that, it's very common to have color+transparency+bump map+normal map, and potentially even more. bundling all of those into a single file allows for away better compression