I think this is more of a planned research breakthrough. I.e. the type that doesn't happen.
I think every research breakthrough is planned. Impact on civilization is what counts. I just have an impression people are not aware of the huge impact Semantic web will have. Why there are no more startups dealing with SW problems?
I think pg's point is deeper than that. Research breakthroughs are made by one or two (usually one) very smart guys. Breakthroughs don't happen because consortiums and commitees declare "let the web be sematic!", which seems to be the case with the sematic web idea.