Seems obvious but the faster speed of work processes over 40-50 years (i.e. deflationary landscape) has ultimately made having a family younger harder. I don't see that pace slowing so a spike in population is doubtful unless technology (and policy as you mention) develops for more later in life pregnancies.
DEMOGRAPHICS IS NOT DESTINY - UPDATE
Seems obvious but the faster speed of work processes over 40-50 years (i.e. deflationary landscape) has ultimately made having a family younger harder. I don't see that pace slowing so a spike in population is doubtful unless technology (and policy as you mention) develops for more later in life pregnancies.