Time have published an interview with Prometheus co-screenwriter where he specifically discusses the end of the the film and where a sequel might lead.
BE WARNED – SPOILERS LIE AHEAD!
TIME: In that final scene, David wants to go to Earth, and Elizabeth wants to go to the alien home world. Where do you think they’re going?
Lindelof: I think they’re going where she wants to go. His fundamental programming has been scrapped. Weyland [the man who built and programmed him] is dead and so now his programming is coming from God knows where. Is he being programmed by Elizabeth, or is it his own internal curiosity now that Weyland isn’t telling him what to do any more? He’s always been interested in Elizabeth, remember that: He’s watching her dreams when she’s sleeping in much the same way that he watches Lawrence of Arabia. He’s a strange robot that has a curious crush on a human being, and when Weyland is eliminated, I think he is genuinely interested in what she’s interested in. He reaches out partly for survival, but partly out of curiosity, and I think he’s sincere that he’ll take her wherever she wants to go.
Thanks again to seeasea for the link!
Prometheus is directed by Ridley Scott, from a screenplay by Damon Lindelof and Jon Spaihts. The film stars Noomi Rapace, Michael Fassbender, Charlize Theron, Guy Pearce, Idris Elba, Sean Harris, Rafe Spall, Logan Marshall-Green, Patrick Wilson and Kate Dickie, and is now on release around the world.