That is a good point.I've thought about that, but I think the reverse may be true, similar to the plots of every Super-human-mutant tv-show/movie. Normals/Mundanes will ban and/or persecute the mutants/x-men/homo-superior/homo-GMOnsis. There will be so many people who are against it for ethical or religions reasons and so few people who will be able to afford it, that I doubt they'd ever be able to get away with such procedures publicly. Privately, they may, but I doubt that any increases will be able to create a sub-species much smarter or capable without being an obvious GMO-mutant, so I doubt they will ever get ahead in government, religion or society and over-turn human nature. Even if one strain did, they'd almost certainly try to fight off rival strains that happen to have different capabilities or a different lineage. While fiction would have us believe that vastly different looking mutants will hate us but get along with each other will work as a metaphor, we need to realize that it is only a metaphor --they will be as capable of intra-species racism as anyone.