We should simply pursue "organic growth" eg. grow as much people as we can care for and educate properly. Unfortunately our elites seem really hell bent of keeping the social landscape hyperconpetitive so the resources we have don't really get distributed... and as a consequence of course (rational) pople have fewer children! Also there's an intellectual war fought on "traditional values" that enabled stuff like extended famimlies to exist and make child rearing at least bearable by sharing the load of caring for the nasty little critters.
Whether we "need" humans depends on where one's values are; for those who would like humans in some form to continue to exist, the idea of AGI making humans obsolete isn't terribly comforting. Even those who might really like the idea of humans sort of evolving into AI (and eventually ceasing to biologically exist) might not be keen to rush toward human obsolescence if they're not thrilled with initial versions of AGI (diversity and optionality is nice).
EDIT+: Counterintuitively, it might be more benefficial to have way more people in the (maybe short) era before the passing of bio-humans, to increase the probability that as many as possible of the valuable human ideas get passed on to our AGI descendents! If AGI is finally achieved by eg. "three middle aged white guys surviving some apocalypse in some bunker", then that AGI will only have and carry on the values and mindsets of those "three middle aged white guys"!!! Ironically, "unification under one umbrella of AGI research efforts" like eg. OpenAI folks try to do increase the likelihood the "three middle aged white guys fathering a narrow-minded AGI", instead of encouraging a diversified competition landscape...
We seem to be handling the upcoming birth of AGI just as well as we "handled" this pandemic...
Thanks for recommending the at section of the document. I’ll take a peak at it. I’m not really worried about yhe birthraye decline case because I think there would be subgroups of humanity with higher birthrates. Both small communities like the Amish and large communities like Nigerians still have birth rates well above replacement level. Africa is industrializing fast and could become an industrial powerhouse like China, if automation doesn’t remove the competitive advantage that high population otherwise would give them. Many African countries GDPs are growing at 10% every year.
This comment of mine goes a little off topic but I think the stuff I’m addressing is interesting and important for predicting the future.