As far as I know, no one has any idea. BUT - I think the premium has a very good shot at being the "definitive" version of the game here, considering that all the things that are in the Premium that aren't in the Pro were a part of Keith's original Archer designs.
So this isn't a case of sticking some extra crap onto a pin to make it premium, in fact it seems as they they removed stuff in order to make the Pro. (The pro is still an amazing incredible machine).
Also the Premium art is supposed to be Egyptian theme, so to me it seems like it will look the best as a whole with the art package. And Powerslave is my favorite album so... pre-ordering the Premium was a no-brainer for me, sight unseen.