Lucas has actually stated that the Special Editions were only experimental versions. To see if the movies with effects would sell well and they did. He never stoped working on the original three Star Wars movies. He marketed the 1997 versions as definitive just for marketing. In 2007 we are getting Ultimate Versions. The statement above is from Ben Burtt. That he is working on remixing the audio. Thats all we know of but it is almost certain the 2004 DVDs will not be exactly like the 1997 versions.