Where things will get interesting is when the replacements exceed the capabilities of the originals, or expand our capabilities beyond anything our biology can do currently.
This Alpha Point is coming soon. I, for one, am looking forward to it.
Yes, the potential for abuse is there. So? Because some people abuse driving cars, should we outlaw automobiles? Same difference here.
Definitely it's still early, primarily focused on replacing failing body parts with stuff that is barely functional. But it's going to get better.
I think the first voluntary modification will be the cochlear implant. As the software that drives the thing improves it won't be long before people can get better fidelity with those than a normally functioning ear. At that point I expect people in the music industry, especially the engineering side of the music industry though some performers too, to get them so they can do their job better.
I'm with you, I'm for it. My primary negative concern is that I can see this as a major driving force behind increased socialism. As people start being able to learn via implants or improve the performance of their body there will be a big wave of people complaining that it's "not fair" overall life improvements are only available to the rich (because at first it will be, like any new inbound technology it's going to have a hefty price tag), and that's going to drive some sort of ill considered government program. It'll make job interviews interesting too, do you prefer the guy with the kickass implant that allows him to "know" absolutely everything about your industry without having learned anything or the guy that actually reads books and might not know as much but will still be able to do his job without a chip?
Yes. And this will happen within the lifetime of many here. In addition to helping the disabled, you will also see people giving up their original, perfectly-good parts for sythentic replacements, like your "organic" eyes for cybernetic copies that look real in every way, plus can see in IR, take fotos, even go non-passive for ranging and targeting data, etc.