As far as appeal goes, I'm guessing the only reason we got the cleaned-up/re-recorded audio on the Blu-ray was because so many people were saying how much better they thought the extended cut was after the Quadrilogy came out. I even recall a few serious review sites posting articles about it being an improvement when I doubt they'd otherwise mentioned the film in years.
But at the end of the day, I can only assume getting Lance Henriksen back in the studio for a couple of hours is considerably cheaper (not to mention far less time-consuming) than digitally overhauling all those effects shots would be. And as the Anthology seems pretty definitive and only a few die-hard fans are likely to double-dip for another release of the third movie, I still say I'd be mightily surprised if they went through with it.