A brief and imprecise history of 20th century SF (with a bit of fantasy) into the 21st:

Back in the so-called Golden Age, it was about rocket ships and blasters and the possibility of an atomic bomb.
Possibilities became reality, and post World War II writers were obsessed with the prospect of nuclear annihilation. Along came the sixties and the New Wave and rather than celebrate technology, feared its dehumanizing potential; mind altering drugs were okay, though. Then it got kind of boring, Tolkien was rediscovered by middle school kids and the fat fantasies started to take off. The cyberpunks depicted technology as neither good nor bad, just something that humans could use for good or bad and was, like it or not, a fact of reality. Then along came things like slipstream, New Weird, New Space Opera (meanwhile, the old space opera and golden agers were light speeding about the galaxy all this while people were accusing the genre of becoming too literary for its britches), Interstitial Fiction and what have you.

So what’s next? Tales of economic doom and environmental disaster? (But wait, wasn’t J.G. Ballard doing that a long time ago?)