Tin House, a literary magazine, asked me to introduce the current science fiction issue with an overview of the field. I wrote them an essay called "Radical Presentism," about the way that science fiction reflects the present more than the future.
Mary Shelley wasn't worried about reanimated corpses stalking Europe, but by casting a technological innovation in the starring role of Frankenstein, she was able to tap into present-day fears about technology overpowering its masters and the hubris of the inventor. Orwell didn't worry about a future dominated by the view-screens from 1984, he worried about a present in which technology was changing the balance of power, creating opportunities for the state to enforce its power over individuals at ever-more-granular levels.
Now, it's true that some writers will tell you they're extrapolating a future based on rigor and science, but they're just wrong. Karel Čapek coined the word robotto talk about the automation and dehumanization of the workplace. Asimov's robots were not supposed to be metaphors, but they sure acted like them, revealing the great writer's belief in a world where careful regulation could create positive outcomes for society. (How else to explain his idea that all robots would comply with the "three laws" for thousands of years? Or, in the Foundation series, the existence of a secret society that knows exactly how to exert its leverage to steer the course of human civilization for millennia?)
For some years now, science fiction has been in the grips of a conceit called the "Singularity"--the moment at which human and machine intelligence merge, creating a break with history beyond which the future cannot be predicted, because the post-humans who live there will be utterly unrecognizable to us in their emotions and motivations. Read one way, it's a sober prediction of the curve of history spiking infinity-ward in the near future (and many futurists will solemnly assure you that this is the case); read another way, it's just the anxiety of a generation of winners in the technology wars, now confronted by a new generation whose fluidity with technology is so awe-inspiring that it appears we have been out-evolved by our own progeny.