I've been telling people for years that in time the PC as we know it will be obsolete, and we'll have personal comuters that we carry with us everywhere. Many of us already do a lot of our personal computing with our phones. Beef up the processor in the phone a little, add a wearable display and a suitable portable entry method (I don't care to argue about keyboards, mind control or whatever, but there will be something) and we will have totally ubiquitous computing.