You can't expect it to have HD800 type soundstage because it hasn't changed the reason it has the soundstage it has. There's surely some wiggle room because of the lighter diaphragm which may also be a different shape/size and more speed/transparency and better imaging will give a more spacious sound, but the pads are the same, and it's still sealed to the baffle because orthos need to be. I'd love to eat my words though.
I have not heard the HD800's but I have read that the soundstage is exaggerated. If it is, then that would not be something to be aspired to. What is you opinion on the soundstage of the 800's?