Back in 1992, Robert X. Cringely wrote in Accidental Empires: How the boys of Silicon Valley make their billions, battle foreign competition, and still can't get a date [Oxford comma sic]:
Fifteen years from now, we [Americans] won't be able to function without some sort of machine with a microprocessor and memory inside. Though we probably won't call it a personal computer, that's what it will be.
Of course, by and large that's true; the American economy depends on microcomputers and the networks connecting them in a very intimate way. It's not obvious in 2007 just how predictable that was in 1992, as the "networks connecting them" had nothing like the ubiquity which is now the case. When "Accidental Empires" was written, the impact of a personal computer in an office was to remove the typewriter and the person trained to type, replacing both with someone who had other work to be doing typing on a system thousands of times more complicated than a typewriter.
What's most interesting though is the (carefully guarded; well done Bob) statement that "we probably won't call it a personal computer," as that part is only partially true. All of the people who have Tivos, or TVs, also have a personal computer. All of the people who have mobile phones and digital cameras also have a personal computer. The people who have Playstation 3s and Nintendo Wiis also have personal computers. In business, the people who annoy everyone else by playing with their palmtops in meetings instead of listening to what the amazingly insightful Cocoa programmer has to say are also wasting time trying to work out how to sync them with, yup, the personal computer they also have on their desk.
So the question to be asked is not why Cringely got it wrong, because he didn't, but why hasn't the PC already disappeared, to be completely replaced with the "it is a PC but we won't call it that" technology? Both already exist, both are pervasive, and the main modern use of both is remote publishing and retrieval of information, so why do we still tie ourselves to a particular desk where a heavy lump of metal and plastic, which can't do very much else, sits disseminating information like some kind of [note to self: avoid using the terms Oracle or Delphi here] groupthink prophet?