Is Proto-Alien in last scene the fabled "Progenator" abandoned from "Alien 3"?

Having seen "Prometheus" over the weekend here in the UK and thinking about the film since then, was the proto-alien we see crawl its way out of the body of the Engineer in the life-boat the fabled "Progenator" Alien that was created for Vincent Ward's "Alien 3"? It looked like a very sleek version of the beast we know and love and could explain how the species kick-started. It also looked very similar to the heiroglyph that the astronauts found at the rear of the "head" room. The only gripe with the film was what the hell was the Engineer doing at the beginning of the film?! Was he sacrficing himself so his DNA would mix the Earth-bound material? Was he left behind by the "Saucer" vessel? Was it Earth? Otherwise, roll on any sequel and a possible glimpse of the Engineer's homeworld.