the only way to "change what it means to be human" in a manner which is distinctly different from the way technological innovation has always "changed what it means to be human" would be to substantially alter the human mind.
not the memory capacity, not the calculation speed, not the auxiliary assets: the mind itself.
The human mind is a mix of personality, reason, emotion, learned habit, and instinct. All hype aside, I don't see technology making any impact on any of the above any time in the forseeable future - with the faint possibility that technology will be used to either temprarily or permanently bypass the limbic system. Some might think that desirable. I suspect the unintended consequences would prove fatal to the modified organism.
All those things are already the target of mind-altering drugs (Ritalin, for example). If electronic modification starts to move in on those areas (first for the purpose of repairing damage or dealing with "psychological conditions"), that would only move us further down that road.
Also, if electronic modifications of the brain start to connect people into some kind of collective consciousness, would that also not alter the fundamental nature of being human?