Word has it that Geore Lucas is something a pack-rat. He doesn't throw away anything. Everything for the original starwars still exists. Don't ever believe what they tell you otherwise. They still have original negatives to starwars in cold storage. Every bit that was shot for starwars is in cold storage. It may not be in one piece anymore, but all the shots still exist. A far as them being useable, probably not, but they can still be used to make new negatives, just like they did for the 97 special edition. Which makes me strongly believe that they have already updated the entire original negatives for future use.

Ultimately, George is still just milking the franchise, and I would not be surprised if Lucas is testing the audience with these blu-rays, seeing how they react to some of the changes. I think this is all leading up to the 3D releases where we could very well see alot more changes.