For reference here’s probably the best comparisons I’ve seen between 2011 1080p releases and the 2019 4K releases.
TPM: https://www.hdnumerique.com/dossiers/819-test-4k-ultra-hd-blu-ray-star-wars-I.html
AOTC: https://www.hdnumerique.com/dossiers/820-test-4k-ultra-hd-blu-ray-star-wars-II.html
ROTS: https://www.hdnumerique.com/dossiers/821-test-4k-ultra-hd-blu-ray-star-wars-III.html
Pretty minor improvements, but still worth it. It will be good to see what AI enhancements can do to the footage.
It looks like some highlight detail was lost in the phantom menace 4K due to over saturating the colors.
The 4K Attack of the Clones actually looks pretty good to me.
For Revenge of the Sith, I think the lightsabers looked better in the 1080p version as opposed to the 4K.