Ridley Scott has mentioned that he hopes there will be a sequel to Prometheus, but so far that's all he is saying. As Prometheus itself isn't released until the end of this week, it is a bit early to get an actual date for the sequel; for one thing, it must depend on how well Prometheus does at the box office. You should be able to find more up to date information here as it comes out.

As Prometheus is very different to all the Alien films, there is a lot of scope here for a whole new series. The premise of this film is the idea, which was popular some years ago, that the earth's early civilisation was constructed by aliens. It is said that Scott got some ideas for this plot from writers like Erich von Daneken, who has written several books claiming to 'prove' this.