Rather than try another sequel, Ridley Scott is returning to the Alien franchise to direct a prequel with a story that skips back to the future's past. We know, it's confusing to us too. Scott told Empire that the prequel won't be directly related to his sci-fi classic.
It's a brand new box of tricks. We know what the road map is, and the screenplay is now being put on paper. The prequel will be a while ago. It's very difficult to put a year on Alien, but [for example] if Alien was towards the end of this century, then the prequel story will take place thirty years prior.
In Alien, Sigourney Weaver and company intercept an alien life form on a planet after it has terrorized a different ship and crew. It would seem that Scott and writer Jon Spaihts aren't trying to connect to that storyline.
Whatever they are planning, it has Scott excited. "I never thought I'd look forward to a sequel, but a prequel is kind of interesting. I'm looking forward to doing that."