Prometheus's Alien connection was nothing more than a cheap marketing gimmick to drag Alien fans into the picture (that's hardly originality), Ridley is really into doing these tricks now. If Ridley wanted to discard the Alien Prequel he was working on in favor of Prometheus, he should at least tell the story with integrity rather than with marketing schemes. The new film is promised to have no "gods and dragons" (aka engineers and aliens) in it whatsoever, you'd think that if Prometheus truly belonged in the Alien universe then there would still be some connection to keep the series going. Being without Aliens OR engineers, what else is there?