In fact, you'll feel so good with the cyborg-injected chemicals that you won't feel the need for mating or reproducing.

Well that's already kind of happening, no? But a lot of people reproduce not because it feels good in the way that sex feels good but out of a longer-term sense of obligation.

just not often listed as an AI risk.

Well I think I would put it in the same category as wireheading. And given the choice, probably a lot of people will do it. Judging by the percentage of the population which declines reproduction in favor of sex with contraception; drugs; alcohol; internet porn; and other stimulation.

But I predict some people won't make that choice, either because they like the idea of reproducing; or because their religion tells them to, or whatever. So I doubt it will lead to extinction, but it could very well re-shape humanity. Which seems to be happening already. If you do the math, ultra-religious types are on track to world demographic domination.