The only real hard constraints on long term population growth are, food insecurity, war, and pandemic.
A secondary cause that is relevant for the aging population example you cited is gentrification, there seems to be an inverse population curve in respect to wealth - meaning the more money you have (or your society has) the fewer children you'll have - this is something that can be overcome thru public policy if deemed a priority by a society.
Because of this, I see no reason why population will not continue to grow world wide - climate change is most likely to change where and what kind of food can be grown, not how much of it we can grow.
A secondary cause that is relevant for the aging population example you cited is gentrification, there seems to be an inverse population curve in respect to wealth - meaning the more money you have (or your society has) the fewer children you'll have - this is something that can be overcome thru public policy if deemed a priority by a society.
Because of this, I see no reason why population will not continue to grow world wide - climate change is most likely to change where and what kind of food can be grown, not how much of it we can grow.