It also leaves out the clear separation between classic Sci-Fi (Clarke, Verne etc.) and modern Sci-Fi(Harlan Ellison, Ray Bradbury, Gene Roddenberry, etc.). Modern Sci-Fi came as a result of the McArthy hearings. Instead of using American society as their backdrop, many writers in the 50's created alien worlds to convey their communist ideals and avoid being blackballed.
Stop and think about Star Trek. A ship full of people who abhor material wealth and go around showing everyone in the universe the correct way to live. Sounds alot like communism to me!
You nailed it. The reason that SF isn't doing near-future predictions anymore is that reality is moving faster than fiction ever did. Gibson was about the last guy to get a leap on it in a big way and look how dated Neuromancer (a supremely brilliant book, IMHO) looks today! That "cyberspace" thingy he made up, for example. Instead of super-hackers meeting in smoky bars to hammer out deals for industrial cracks, we have grandmothers searching the 'Net for quilting patterns. Tough to get a novel out of that...