Much talk is now centered around our next great 'evolutionary step' forward. Whilst some have put this firmly in the AI (Artificial Intelligence) domain, there is also the argument of IA (Intelligence Acceleration). One way to see this is a merging of information technology and the human, so that a 'superorganism' will be achieved. One that will have instant access to information and thus the 'two heads are better than one' will be exponentially increased to a 'global' head.
An interesting essay to this end is Evolution & The Internet: towards a networked humanity.
It is possible that a symbiosis may be the result of the 'Technological Singularity' - a merging of intelligent humans/machines rather than as a race of machines that take over. The singularity could more likely be a mesh - a symbiosis - between humans and their use of intelligent artifacts in order to foster their own intelligence acceleration instead of passing the intelligence over to silicon agents.
In short, the human still has much growth left. Only if we consider the potential from an external point of view will the alternative of machine-intelligence seem the most plausible. If we can recognise the inherent possibilities within increased information within the human species, and the acceleration in intelligence this could produce, then the future of human evolution is with the wise.
As Jonas Salk - the Nobel discoverer of the Polio vaccine - put it: our future will be about the survival of the wisest.