Overconsumption and overpopulation are intertwined. The prospect of 10 billion people or more living as we in the developed nations do now is frightening but unrealistic, I think; environmental degradation will crush that aspiration before it can reach full term.
Most population growth is happening in the developing world. The clue is in the name - many developing nations are on their way up. Endeavouring to curb population growth can only be a positive thing. Many of the actions we could take are intrinsically humanitarian in themselves.
As a nation, we need to completely change our attitude to what is 'old', and by doing so we can also change our attitude to what a fantastic resource older people are; they're not a drain on our future, they are potentially really valuable resource in themselves.
There is about a 20 percent chance the world's 7,000,000,000th human inhabitant will be born in India - by far the highest chance for any individual country. If so, let's hope for a girl, although that chance would be less than 50 per cent...