I agree with you -- decades of psychological research show that people acclimate to what they have, and then want more.

Imagine cavemen postulating about what we'll do when we have these big machines that can carry us around at great speed, and when our food is already made for us and no hunting is required. Could they have guessed we'd work in glass office buildings so we can buy iPods and McMansions?

I suspect we're in no better position to guess how we'll use our future economic output, only that we will definitely want to spend it.