1. 11 billion may be too much.
2. This isn't uniform across the globe. Japan's population is shrinking due to a very low birth rate, and that may be a bad thing (loss of cultural and genetic diversity, for example). And this is the more relevant aspect given the context.
Color me skeptical. If previous prognostications are and indicator, humanity in general cannot predict the future more than 5-10 years out with reasonable accuracy.
Another way of saying this is that the confidence interval on global population estimates 80 years into the future is most likely large enough to render the estimate meaningless.