This picture provides a nice summary view of straight extrapolation from known events.  There will be hiccups, and odd things along the way, but directionally this is not a bad model to have in the back pocket.

Given that few predicted how Web 2.0 would come to be defined during the early stages of Web 1.0, the concept of Web 3.0 is still a bit fuzzy, and Web 4.0, the WebOS on Nova’s map, is really hazy. The WebOS implies that machine intelligence has reached a point that the Internet becomes the planetary computer, a massive web of highly intelligent interactions.

Source: » From semantic Web (3.0) to the WebOS (4.0) | Between the Lines | ZDNet.com