Lucas has done everything he could to make sure the original would not be re-released. He hates them with a burning passion for some reason, and frequently insists that the redone versions were his 'real' unrestricted vision; even though the only differences are ridiculous things that have no real merit.
According to popular theory, when Lucas released the special edition he did the cuts and edits to the original negatives, making it impossible to use them. This leaves only the Library of Congress versions of the original film in tact, and I don't see Disney going through that much effort.
About the only way to see the original is to hunt down a VHS; if Lucas hasn't destroyed them all with a chainsaw.
I thought the originals made it to DVD as part of disk 2's for each of the "special edition" ones. Basically the VHS movies pressed to DVDs. Or Netflix sent me some bootlegs a few years back.