"We are slowing down population growth because of education, gender equality, the rural-to-urban transition, and birth control." You forgot AIDS. And they are developing medicines for it. "And in order to ensure that the developing world's economic growth continues, we must ensure that we transition to a new energy economy and avoid major nation-state wars."
Ensuring economic growth quite probably ensures ecological footprint growth. So we will eat our natural reserves without having tens of billions of population. And why would civil wars be any better? The western world with modern arms probably would not take population bomb as their own problem. What does it matter then? Human suffering in developing world because of starvation. They are developing aids medicine, global warming is decreasing arable land area and so is erosion. And fertilizer prizes are probably going to rise.