There has been evidence of this new remastered original trilogy slowly building online over recent months. This is due to the restoration company posting short clips to a quiet unknown YouTube account.
Check out this video on an explanation on what has been happening and a comparison between the new remaster and the current 4K discs.
TLDW: The new remaster looks way better than the current discs.
Then check out this 17 minute compilation of remastered original trilogy clips that have appeared online so far.
Wikipedia has a list of them (most of them, at least. I can’t speak for its completeness): https://en.wikipedia.org/wiki/Changes_in_Star_Wars_re-releases