USD is at a higher level of abstraction than gltf (IMO). It was created to ease things such as scene graph LOD (levels of detail) for example. It's made for very large scenes. It was created as a file format to exchange very large scenes for 3d animated movies. Inside of a USD file you can point to many other files, for example GLTF, OBJ files etc.
It seems like a great format so far, but I'm skeptical based on Adobe, Apple, Autodesk track records for "open" formats.
"Well-known file formats for interchange in the VFX industry like OBJ, FBX, and Alembic primarily deal with interchanging flat/cached geometry, with no facility for assembling assets or editing the data directly. USD does serve the role of an “interchange file format,” more comprehensively than previous public efforts, because it already interchanges not only geometry, but also shading/materials, lights, rendering, linear-blend skinning and blend-shape animation, rigid body physics, and is extensible along numerous axes."
It seems like a great format so far, but I'm skeptical based on Adobe, Apple, Autodesk track records for "open" formats.