Education will pay as it always had in one way or another. What Krugman describes can be called a demise of the liberal arts college (who needs economists or lawyers or financial innovators of hedge fund type anyway), a demise of the UNIVERSITY (sufficient education could be obtained during schools years, perhaps by extending it by a few years, followed by a technical school, a model used in the Soviet Union), or perhaps a decline of the US, as it gives away its technological edge to some other country and turns into a third world dump, where a handful of elites rule over uneducated powerless masses. In the last case, the Krugman of 2096, he should dream of escaping to the next beacon of technology and democracy.

Unless you are willing to imagine a complete collapse of a society into a dark disorganized  tribal land, there will always be a need for highly specialized highly educated people who maintain and control the technological underbelly: engineers, doctors, agronomists, teachers, accountants, etc. These people have always been there, in the sense that every organized society - Egypt, Mesopotamia, Rome, Chinese dynastic societies, societies of the Americas - had these people and could not function without them.

As to plenty food - no farmers, that's just a particularity of the US, although it would be incorrect to believe that there are no farmers in the US or that there is a direct causative relation between the two (doesn't France have plenty of winemakers and lots of wine? And US does not have that many small business either). But how about plenty food - plenty of agricultural specialists. The US has something called the Agricultural Research Service, plus a network of university-based agricultural support centers (cooperative extension service). So when honey bees began to disappear last year (Google for more info), beekeepers could quickly ask for help from a large number of agricultural entomologists.