The age of the cyborg is already here. The medical implants like pacemakers, artificial hearts and cochlear implants, as well as the constant advances in prosthetic limbs mean we are already making cyborgs. They may not be the "stronger, faster, better" Six-Million-Dollar-Man type, but you can hardly look at someone with a hearing aid literally plugged into a port in their head and tell me cyborgs are pure science fiction.
Mokalus of Borg
PS - Perhaps we do need to worry about the ones that improve on humanity.
PPS - Or maybe they'll be unspeakably awesome. Who knows?