In addition to the D750 camera, SB500 flash and Nikkor 20mm f/1.8G FX lens (see this post), Nikon will also announce a new MB-D16 battery grip for the D750. All of those products were confirmed also by digicame-info (they always get correct information right before the announcement). Expect the press releases to be out around midnight tonight EST (Thursday) or early morning Friday GMT.