We already went from "the Net" to "the Web" to "Web 2.0", just by changing the software, and Brain 2.0 isn't far behind.

How much of the change from "the Net" to "the Web" to "Web 2.0" is actually noteworthy changes and how much is marketing? I'm not sure what precisely you mean by Brain 2.0, but I suspect that whatever definition you are using makes for a much wider gap between Brain and Brain 2.0 than the gap between The Web and The Web 2.0 (assuming that these analogies have any degree of meaning).