With the release of Blu-Ray or HD-DVD technology, future Star Wars re-releases will be accompanied by a large amount of behind the scene footage. McCallum said every aspect of the filming process was recorded for future documentaries but could not be included because of the limited amount of space on DVDs.

The HD-DVD format supports 15 gigabytes of space and Blu-Ray supports 25 gigabytes, according to blue-raydisc.com. The current DVD format can hold only 4.7 gigabytes.

http://www.dailyevergreen.com/disp_story.php?storyId=15209

But its such a lie, LOTR did it with two disks. They are just holding out