I'm talking about things we can do right now to deal with the potential of population growth.

Obviously if we cure old age, or start uploading ourselves to computers, or genetically engineer ourselves into something different, or fundamentally change human reproduction technologically, we would be in a completely different situation and would need to come up with new solutions. But I'm not sure we can really plan for that until we actually see how that would unfold; and, in any case, in any of those scenarios, we would be better able to deal with the consequences with a world population of 9 billion then with a world population of 12 billion.