haha i've wondered this too, but we'll just have to wait. The cinematic cutscene is supposed to of happened 15 years or so before the events of the game. If it was Mor Dhana then we assume the garleans crashed into sometime within the last fifteen years and ruined it. If we didn't get lore that way, it may be the unimplemented zones that are in our lore but not in the game actually like Xelphatol and what not.