Alien 5?

Sigourney Weaver told Sci Fi Wire in a recent interview, "Ridley Scott and I have talked about doing a movie where we'd go back to the original planet and get rid of them once and for all," Weaver says "I'm not sure where my allegiances would lie, but that would be the main reason why I'd be curious to go back and sort of see inside of Ripley who would win."

Even though everything sounds like it come together, she said it still not absolute, "I'm not very organized, and I'm always pretty busy, so it's not like I'm writing the treatment and sending it to Ridley and saying, 'We've got to do this,'" she said. "I think it's an interesting series, but I'm happy with what we've done. We haven't compromised it. I really did die [in Alien 3] to avoid any contact with Alien vs. Predator. That was why I disappeared after the third one, because I'd heard that was an idea."

Source: Sci Fi Wire