I think that the more overpopulation there is, the more people feel stresses from it, leading to more dissociation and distraction from embodied awareness, and more wishful thinking for an escape. Both of those create a fertile ground for ideas such as the notion that escaping into a computer fantasy existence, and/or modifying their bodies by adding machines, offers some form of escape and isn’t noticeably horrifying in contrast to how horrifying their everyday context is due partly to the overpopulation.
Of course, overpopulation is only one of the sources of stress and dissociation.
As for predictions of what trying to “fuse” human and machine will do to people, I think it will further dissociate and/or actually kill them and replace them with a machine or cyborg that may externally resemble them. And yes, reduced or eliminated natural reproduction may be one aspect of that.
But the overpopulation may continue anyway, as the same kind of thinking that leads to wanting to fuse humans and machines, tends to also want to mess with genetics and breed people and other animals in factories.