How is that going to work though? We're likely way past the carrying capacity of the whole planet-wide mesh of habitats, even if we make some huge technological

How is that going to work though? We're likely way past the carrying capacity of the whole planet-wide mesh of habitats, even if we make some huge technological leaps to reduce our adverse impact on the biosphere – right now, the combined H. sapiens biomass is about ten times that of all other non-livestock mammals combined, and just the space we take up is driving lots of other species to extinction. Cure aging and this will grow ad infinitum and likely outpace anything we can do to lessen this. I don't see people stop having children, most people are incredibly strongly wired to want them, and they're pretty important to how all our societies function. So either you keep this cure away from most, creating an impossibly dystopian society of immortal lords and mortal slaves, or hope for a miracle like a terraformed mars within a few generations, or things are bound to crash horribly at some point probably not too far off.