Just checking: you do know that there is a difference between change of "5 standard deviations" and change of "5 IQ points". 5 standard deviations is equal to "1 in 3.5 million", which makes your claim fairly farfetched with the tech of today or of the future decade or two, especially given how IQ is much more function of nurture than of nature.
I am aware of this. Genetic engineering implies far more power than Gwern mentions for one round of embryo selection. 5 standard deviations may sound a lot for you, but in animal breeding we have changed the distribution of various traits by far more than 5 standard deviations. Into the dozens.