I like your stuff, but this is pure nonsense for several obvious reasons:

1. The corporatocracy is driving the world back into neo-fuedalism. Governments are already slashing budgets, cutting services, and privatizing in the name of austerity. Life expectancy is decreasing. The misery to come suggest the UN 11-12B figure is correct.

2. Even it we did hit 4 billion by 2100, we'd still be overpopulated. (The planet can only feed 3B without Haber-Bosch.)