At the onset of the Industrial Revolution, I don't imagine people could answer similar questions if asked. If we managed to absorb most of the Western world's farming population into massive cities and created entirely new industries, who's to say the same can't be done now?

A massive part of the planet is still "underdeveloped". As these countries emerge from their eternally-emerging state, there should be no shortage of demand that high-skilled workers in developed countries can capitalize on. Creating intellectual property is an extremely rewarding enterprise and one that can be sold to other less skilled nations (as is already the case).