The Droid branding, if it is the real deal, is usually limited to Verizon devices, which means that the Droid HD would land on Verizon most definitely. Based on the size and sim card slot alone, it is probably not a 4G smartphone at all, and more than likely a worldphone.
As BGR comments, and we tend to agree, if the HD is a 4G device it would be the thinnest to date, and would represent some serious strides in 4G technology. Definitely an impressive step forward if that is the case.
No word on when the Droid HD will arrive on store shelves, but with images out in the wild it could launch in the coming weeks.