Most movies finished as a DI are only done so at 2K anyway. The theater gets it as a 2K file on a hard drive and the 4K projector upscales it.
I was unaware that the C4 saga screening was done using a commercial cinema projector. IV-VI were only cleaned up at 1920:1080 HD resolution (although the source scan was 1828:1556 which is considered a 2K harvest of the "squeezed" anamorphic image on the negative of true cinemascope movies like the OT and TPM). The Lowry guys were very specific about that at the press conference in 2004 (with Hamill, Kershner, Jim Ward et al) when someone asked if it was 2K. They also specified full RGB resolution, which makes sense since they were doing this on 600 networked powermacs. I can only assume they meant 1920:817 for the actual 2.35:1 image itself. Either way, 1920 is still slightly below the 2048 of true 2K.
This info about the C4 screening, coupled with the fact that GL did go ahead and make additional changes to the Lowry master for the blu-ray, makes me wonder if he really did intend it as the basis for any and all future releases of the movies. Now that it's Disney's property, I would assume they'd want it transfered in a quality greater than just hdtv/blu-ray.