There are a lot of things that biological organs can do better than man-made equivalents. This is primarily a matter of energy efficiency. However, man made organs such as muscles would conceivably be considerably faster and stronger.
This too extends to the brain, which for all its massive parallelism, is actually very slow and bulky for what it does. It can be anticipated that it would be possible to eventually copy a human mind-state to a man-made processor unit, probably one specifically designed to house a human consciousness. It would also be logical that these brain-boxes could and would be much faster than a human brain.
Basically the neurons of the human brain perform in a known manner. If we get to the point where we can physically map the neurons, their junctions and their state of polarisation, we can in theory duplicate the organic network to a man-made device, implicitly duplicating the organic mind-state. From there, by increasing the clock speed, we can increase the speed of thought to many times that of the speed of the organic brain.
In a world such as this, the boundary between the virtual and real worlds would be blurred. In the virtual world, the only things of any scarcity are processing power, memory and causality, while the physical world has many more limits, though the virtual world is inextricably dependent on the real.
In the real world, we would need bodies. Having human origins, these would likely be human-like bodies, but mechanical bodies would be more durable, more easily repairable, and more capable than organic ones. The probability is that these bodies would be cyborgs, with a bioengineered organic skin designed to interface with the almost-entirely mechanical bodies beneath them, as well at to be more robust than a genuine organic-human skin. We will probably want to look human to allow physical intimacy, but it is not strictly necessary that the organs involved actually be genetically of human origin
With an increase in available processing power, it is likely that the last secrets of the human brain will be cracked, and it will become a feasible matter to create new child mind-states based on parental mind states, or in isolation. Even reproduction can be mechanised and can also be separated from physical intimacy.