The prequel will be about the origin of the xenomorphs (aliens), which has the possibility to be intriguing and terrorizing — or bland and ruining their appeal. I’d lean towards the former considering the creative forces behind it at work.
“The film will be really tough, really nasty. It’s the dark side of the moon. We are talking about gods and engineers. Engineers of space. And were the aliens designed as a form of biological warfare? Or biology that would go in and clean up a planet?”
-Ridley Scott [The Independent]
Personally I’m hoping that it’s an “act of god”, where it’s simply biology’s way to clean up a planet. The xenomorphs being a man-made biological weapon would cheapen it.