There is a 4K version out there as the library of congress made a copy. Lucas films just stopped them from showing it so far.
This is incredibly innacurate. The LOC can legally publicly screen anything in their collection without permission from any other entity. They choose not to do anything that might rile lucasfilm for fear of damaging a very good working relationship with the company. With a few notable exceptions that we obviously care about, lucasfilm is actually one of the more generous an accommodating studios that the LOC works with.
The scan the LOC has done is a 2k scan of the copyright deposit print that they made for archival purposes (their goal is to scan every piece of film they have for future preservation). It is NOT a commercial scan and it WOULD NOT be used for any sort of home video release.
The truth is, while it’s great that the LOC has copyright deposit prints of all three original films, none of them are pristine (well, ROTJ is pretty close, but Star Wars is pretty pink, and ESB is blood red). Star Wars was a release print that was only sent to the LOC well after initial release (likely sometime in 1978) and it shows all the wear and tear from being projected many many times. And ultimately, some of the work being done by this community will generate far better results than the scans the LOC has done/is doing. They aren’t using multiple prints. They aren’t doing any cleanup. They are just doing raw scans of each print, with basic color correction in the case of faded prints with the sole intent of making a digital backup copy of what they have. It’s not a restoration in any sense of the word.