I still think it's a window/viewer combination.
Why? I don't see any real evidence of that in any of the pics, and there is no window on the outside of the ship from what we've seen.
Judging by the looks of the 'viewer' in those promo-picture, the Kelvin's bridge-module and the fact that we haven't really seen the Enterprise's bridge-module clearly.
Indeed, it's too early to discount the evidence for it being a window at this point.