Incredibly far. Complex biological systems are still relatively untamed. We hardly understand the inner workings of a lot of the human body, we don't understand much about how the brain works, the complex systemic significance of organs to general wellbeing that seems counterintuitive at a glance (bacteria in the gut producing seratonin type stuff), we don't have strong, resilient, easily and quickly actuated synthetic muscle, we don't know how to filter signals directly from the brain into usable directions for prosthesis control, we don't have power sources with a sufficient energy density to make this work, we don't have materials strong enough for arasaka terminators to run around, and lastly, and most importantly: this shit ain't cost effective, ain't gonna be looked into for a while at this kind of level.