The new DVD's will likely be sourced from either the 1985 interpositives (last used for video transferring on the 1993 laserdiscs). The official audio track for the 35mm theatrical releases were Dolby Stereo, with only the special 70mm prints getting 6-track magnetic.
The restorations in 1997 likely consisted of the following (for Star Wars mainly):
- Original camera negative to Star Wars is heavily worn and damaged (several sections are torn or unprintable)
- This is restored as best as can be
- Some sections taken from the 1985 interpositive to replace the damaged areas.
- A new interpositive is created of the restored o-neg, with the replacement interpositives (which were scanned digitally for repair) and new digital shots spliced in.
- From the new interpositive, new duplicate negatives are created for theatrical prints.
Thus, I'm fairly certain the DVD's will use the 1985 interpositives, but they'll still look quite good. The only problem is that the LD transfers a lot of people have been using for fan edits may seem "better" only because they aren't as detailed and current.