The Phantom Menace was shot on 35MM so that can be true 4K, however the other two prequels were shot digitally and not even at 1080p
TPM’s effects weren’t done at 4k though, so most of the movie will still have to be upscaled. And since they probably won’t go through the effort of replacing the handful of VFX-free shots with native 4k material, I’d even guess they’ll just upscale the whole thing.