A key trend that supports his claim is the drastically lower birth rates in more developed countries - it appears that as consumerism and perhaps, indulgence, rise, children become more and more scarce. The data however, is incomplete. We have no endpoint data, and so we are merely speculating about the future.
My own freshly formed opinion is that the consumer will not go extinct, but be assimilated. As Islam, India, and China rise, the western consumer will mix in among them and become their descendants. They will move toward our consumerism, we will move toward their work ethic, their pragmatism.
In an interaction between 500 million and >3 Billion people, Newton's laws of motion apply as though we were free floating masses. At a higher resolution, 500 million is 300 million with several smaller groups floating around it, and each of the 3 billion is split many ways as well - the interaction will be complex and the outcome incalculable. I think it would be neat for someone to make a simulation of that sort.
Anyway, again, good link! I haven't read edge.org before.