Not that I have blind faith that the OT will be fixed, but the theory about the BD trailer having new TPM shots but old OT shots could theoretically make sense...from a certain point of view.
Since they have to do new transfers of all six films, logically they started with the Prequels since those are the newer films and will require less effort to transfer, especially with AOTC and ROTS already having been filmed digitally in the first place. Maybe they're done transferring the PT but are still working on transferring the OT, so all they had available for the trailer were the original DVD versions.
Plus, putting aside image quality, the editing of the entire piece looks like it was done more for advertising purposes rather than an actual demonstration of the BD transfer. Watch it from a strict marketing perspective - the shots they chose are the ones you'd expect to see in a promotional piece - action sequences and iconic imagery.
Again, not saying I expect the OT to look better but until more info comes out, there's still a grey area (blue area? :-)p ) in the final treatment of the OT.