We're halfway there right now. Around half the human body could be physically, totally replaced with acceptable average of use. Kenny is half human, half bionic. He works the extensors of his wrist telling his hand to open. Now whether he has a hand there or not is irrelevant.
Muscles still fire.
I don't know. No one really knows for sure. A good guess is within the next 50 to 75 years we'll definitely see that, absolutely definitely see that. The design at this point is to make things better. Obviously we're trying to look at what can we do to the human body to make it better, faster, stronger, quicker, more agile, and I think we're on the frontier of that right now.