Right from the beginning we have a few problems. We don't really know what human intelligence is and we aren't capable of building intelligent machines. However, lest that obstacle prevent us from moving forward, let's consider what such a thing really means.
If we take the normal distributions of IQ, then it would suggest that about 0.13% of the population has an IQ aboe 145 and 0.003% has an IQ over 160. Using the latter value suggests that in a world population of 6.7 Billion people, we have 201,000 geniuses living among us. Now before we go any farther, can anyone reading this, name one? Can you name what contribution they may or may not have made to human progress?
My point is not to trivialize whatever work they may be doing, but rather to suggest that such high intelligence isn't automatically recognizable except within a very narrow sphere of influence and despite the claims of transhumanists, the bulk of human progress occurs with normally well-educated people that simply work hard.
However, the real problem with the transhumanist perspective is that at the core, they want to eliminate normal human variation from intelligence. If augmentation can be artificially gained, then ultimately everyone would be the same intellectually.
At this point, all human development would stop. The complete uniformity of intellect would create an environment where there can be no meaningful use for teachers. What would be the point in writing a book about any new development, because it would be knowable to everyone without effort. There would be no skill that someone could have that couldn't be artificially gained, so there is absolute equality among all people.
Since we don't actually have a working definition of intelligence, the problem of creativity and emotion still exists, so we have to presume that some people may be more creative than others, so how that fits into superhuman intelligence isn't clear. But, if creativity and insight is the missing ingredient that produces genius, then transhumanism will have failed in successfully augmenting intelligence.
The role of emotions is even more difficult to assess, since humans are not a logical species. While people are certainly capable of being logical, they operate as much from an emotional and belief systems base than anything else. This can be seen by our cultural, political, and religious differences, each of which would still be intact.
Of course, this raises the question of any nation that actually achieved such a capability being altruistic enough to share this technology rather than simply exploit it. Similarly, among individuals, it would require a level of altruism to avoid exploiting those than don't have such augmentation.
However, let's consider what implementation of this would actually mean. Gaining worldwide cooperation for the eradication of smallpox, was not trivial and was often quite heavy-handed in achieving its goals. Would such augmentation be mandated? What would it mean for those that elect to not participate?
I would suggest that an even more fundamental problem exists in describing intelligence, namely what does it mean to comprehend an idea? It's easy to toss off the notion as something that will be taken care of by technology, but it begs the question about what kind of intellectual capacity actually creates comprehension? It certainly isn't access to information. Perhaps it's some element of creativity, but in truth we don't know.
This leads me to conclude that even if transhumanists could successfully bring together the technology and human intellect, ironically it wouldn't change anything in any meaningful way. The primary reason, is because we already have all the information we need. It's in books (or pick your favorite medium). We can look up anything we like and determine an answer or obtain an opinion, or review current work. However, unless we have the comprehension of the subject, it doesn't help much and, as such, neither will any artificial technology that primarily looks like it will be a data storage device.
At the end of the day, the point is that there is no technology that will ever allow me to share my thoughts with someone else. I can try and express my ideas and viewpoints, but I can never convey the essences, the history, the multitude of factors that gave rise to my perspective because that's what makes me a person. When someone else hears or reads my ideas, they will integrate those into their own sense of "personhood" and the idea will have "evolved" just a bit.
Transhumanism's desire to augment intelligence isn't about improving human beings. It's about quick, easy answers to the complexities that have motivated and driven humans to achieve what they have. In effect, it's the lazy approach to the future and, for myself, I think its a cop-out.