Technology

I could definitely see this having an impact, how great that impact is would depend on technological advancements and social factors. Populations are already on a decline in many countries for myriad reasons. The only arguments I've seen about this being a bad thing are primarily focused on the ruling classes concerns, i.e. "the economy." There maybe some mild concerns for the average person, but if we survive what we've done to the planet, overall I think it will be beneficial in the long term for the world population to decrease. Marriages are also in decline, but if all that a marriage is based on is sex, that probably isn't a marriage worth being in. IMO, our species going quietly into the night isn't the worst future, lol.