The way I understand it, Fox owns the global distribution rights to the original Star Wars film (i.e. EP IV before it was EPIV), with Lucas Film (And now Disney as Lucas Film's owner) having the rights to distribute everything else. Therefore it would have been very difficult to release the original trilogy without any of the subsequent special edition fix ups since fox and Disney would have to work together. For years Lucas Film have said that the originally restored film for EP IV was destroyed during the digitisation for the 1990's special editions.
Now that Disney are buying the relevant part of Fox, one company will own the distribution rights to all of the original three films, making it a lot less complicated to release the whole unedited original trilogy. Now the question of "Could it happen" depends only on if its true that the original film/original films unedited digital restoration still exists. The will it happen is harder to answer.
Ars Technia had an article on this very recently. I'm sure a quick search using your favourite search engine will find the article I got most of this from.
