The first thing that was logically done to create the SE's in 97 was to digitize the theatrical cuts of the films. They had to get them INTO the computer before they could start making any changes. So logically, the OOT already exists in digital form. Whether that form is up to 1080p standards, I don't know, as the conversion would be over 10 years old at this point, but I'd imagine it's close to it considering the nature of the process and why it was being done in the first place.
I gotta go with the feeling that something is in storage for a proper OOT release, he's just waiting until he's milked the SE's as far as he can. I mean, if you go back to the various interviews over the years of the creation of the OT (77 to 83), how many times did he start contradicting himself about where the story was headed and that that direction was always his intention? Old habits die hard. He's trying to constantly come out looking like the conquering hero in spite of all the numbers showing how many soldiers he's lost.
And one more thing to consider - ANH was one of the first 25 films inducted into the National Archives as historical achievements in motion pictures...this was LONG before the SE versions, so logically a pre-SE version of the film still exists somewhere outside of Lucasland. That could always be dug out of the archives and given a new restoration and transfer.