People are living longer, immigration can't solve the problem, people are relatively healthy and wealthy, etc. but there is not enough babies entering at the bottom of the pyramid to grow into tax payers to continue funding the social systems.
Dystopian me sees a world where western governments will have to institute mandatory, two child per woman births, moratoriums on birth control, huge incentives for people with children under 18, and aggressive pushes for couples to raise adopted children and/or make new ones.