I think the major problem with their assumptions are that they assumed that culture would stay exactly the same: same speed of technological invention and same educational emphasis on technology over being fscking morons, and same core family - housewife and working man. If they were right, our society might've gotten like that. Though I think the problem is that the more advanced we get, the easier life is, and the easier life gets, the less people feel the need to become smart to succeed, so our advancement gets slower.
Interesting read.