In an interesting post, Dominic Lukes asks if science fiction authors dream of dictatorships. It is an interesting question. Certainly one of the examples that he gives, Robert Heinlein (author of Starship Troopers) is a noted Libertarian. So there is certainly something to this.
But I think the key issue is that science fiction authors are, at least partially, about social criticism. Look at the more recent series of Battlestar Galactica, for example. Or the novels of authors like Mercedes Lackey or Elizabeth A. Lynn that dealt with gender in a very sophisticated way.
So I think we can find all sorts of extrapolations and thought experiments in science fiction. This is, in my opinion, the real strength of the genre and its most important function.
[and yes, I am one of those people who sees Fantasy as utterly distinct from Science Fiction; and Star Wars was a Fantasy]