Wouldn’t 4K be more or less pointless for TFA and RO? Movies like that are always mastered in 2K to begin with.
Rogue One’s DoP Greig Fraser confirmed that the movie was finished in 4k, but it’s unclear at what exact res the vfx were rendered at. There’s still a decent percentage of the movie that’s entirely in-camera, and they used the Alexa 65 with Ultra Panavision lenses which means there was still a good 6k worth of detail for those shots even after they cropped a little off the sides to make it 2.40:1.
TFA turned out differently, at least going by what I’ve read. Abrams’ editing process didn’t give the vfx people enough time to render out the shots at as high of a res as they otherwise could have, and since that’s most of the movie I think it’s effectively stuck in 2k.