I think he is saying that we have already reached the point where elective amputation has entered into our social consciousness because there are already people who are willing to do it.
It should be noted however that apotemnophiliacs (people with BIID) don't want their limb to be replaced with a more functional prosthesis. The whole point is they feel like they should be amputees, so its not really the same thing. It will be different when rational people without any mental illness (as I believe apotemnophilia is) willingly choose to undergo amputation to gain the benefits of an improved cybernet limb.
And interestingly enough, one of the main activists for BIID is a psychoanalyst named Gregg Furth who is also an apotemnophiliac. He and Robert Smith (a Scottish surgeon who actually performed a few of these amputations before the NHS shut him down) wrote a book about it.
Oh, and if you're still curious
Demerzel there is an interesting
article about it.