Nearly every science fiction writer I've hung out with or listened to has asserted that his or her business was not predicting the future. They might write about it, but the purpose of writing about the future is not, usually, to say "this is going to happen" (as if they were fortune tellers gazing into crystal balls) but rather to say "here's an interesting projection of what might happen." That's true, but it's incomplete.
Sometimes writing about the future is a way of warning people "If This Goes On..." or saying "Your way of looking at the world is not broad enough; we see things differently." Writers who want to do prediction often do so outside of their fiction. Famously, Arthur C. Clarke wrote about geostationary communications satellites, but he did so in a 1945 scientific article. I was pleased to play a small part in Bruce Sterling's Viridian Design Movement an artistic online commune dedicated to discussion of what a globally warmed world would be like. (*)
So it's fair to say that a writer doesn't write to predict. But SF writers do predict, and sometimes they predict with real clarity, bringing together threads that are loose in the wind and saying "here, this is pointing to THAT." In this category I give you Cory Doctorow's speech "The Coming War on General Purpose Computation", given at the recent Chaos Computer Congress in Berlin.
It's about the first half of the recording's hour. Go ahead and watch it. I'll wait...
Done already? If you're not convinced that he's right I probably can't add much. His recapitulation of how we got into stupid copyright wars, and how copyright wars are going to morph into a war on general computers is both scary and, I fear, scarily accurate. Like much good prediction it's not far-future and believing it doesn't require any leaps of faith. You just need to perceive what's been going on, and going wrong, in the last decade or so, and realize it's not going to get better, it's not going to end peacefully; on the contrary, it's only going to take off. A few weeks ago I suggested that 2012 would see a revolution in drug manufacture; what Doctorow is saying is that the next decade will see a revolution in every industry, from biotech to automotive to medical devices and anything else you can think of.
Doctorow ends on an optimistic note. I hope he's right.
(*) Don't believe me? Google "Wexelblat Disaster". Yes, that's me. I was moderately appalled to discover that was my Wikipedia legacy.