It's sci-fi, I'm positive. My definition of sci-fi is the basic question : What would happen if...? The author of the Left Hand of Darkness wrote that definition and I've stuck with it since.
All good sci-fi delves into this. Anything else, I would personally classify it more as fantasy or epic. Like Chronicles of Riddick, doesn't actually answer this question, so it's kind of a more techno-fantasy story than sci-fi.
I'm probably going to get flamed for this, but so is Star Wars. It clearly falls more into the category of epic fantasy, as it deals with good vs. evil in a fantastic universe that doesn't fulfill my premise.
As compard to Minority Report: What would happen if, cops could prevent murders before the happened?
And Shadowrun : What would happen if magic returned? Valid, even though magic is unsubstantiated, but it still deals with its effects on society and tries to define magic in a scientific sense.