It would seem that GL is sticking a little too close to the formula for the release of the Indiana Jones trilogy.
While there was little documentary footage available for IJ, there is plenty of it for SW, but NONE of it is part of this release. It has some new documentaries and a lot of previews related to EIII.
Basically, GL had not planned on releasing the OT on DVD until 2006 or later. With the success of the IJ release on DVD, he is putting out a similar release to meet some of the demand as well as promote EIII.
I would expect a future 2- or 3-disc per movie set to be available in the future that includes the title-specific making of documentary, deleted scenes, casting videos, frenzy surrounding the release, etc. Of course, who knows what version of the film will be on them.