Far from abandoning all hope, we have the choice to orchestrate a reduction in our numbers during the next ciuple of centuries by planned reduction of the birth rate or having nature reduce our numbers by starvation.

I see a longterm globally decreasing population trajectory as being extremly difficult to achieve politically. Think of all the local perverse incentives. For example My local/regional group has the only true religion, and it is god's will for it to expand at the expense of the infidels. It would take some pretty draconian global government to suppress such instincts.

Assuming a reasonably non catastrophic population trajectory can be extablished, I think it is an open question what sort of population and living standard can be sustainably maintained. Presumably we will retain (and probably advance) science and technology, and that should allow equilibrium levels much greater than in pre-agricultural time. I don't believe fossil fuels (including fission) are the last word in energy, i.e. in some form renewable enrgy technology should allow the continuation of some level of industrial energy usage. But I guess we have at least a couple of centuries to answer that question.

Next couple of centuries? I think the wolf is at the door now, and well before mid century (2050) the population reduction will be in full swing. I don't see it happening as some sort of rational response, but rather an enforced consequence of being extremely out of balance with the ability of the earth give us the opportunity to provide for ourselves.

Looking at is as a couple of centuries seems to me to be a convenient way to think that the problem is far in the future.