Everyone seems to be making a leap from high IQ --> dominating the world. Sure, your average world leader is probably has a higher IQ, on average, than her constituents. But this relationship is not causal, nor is it reversible. Simply making babies "smarter" is not going to result in them ruling the world in a few years and causing massive generational strife. If you'd like examples, I recommend checking out a MENSA meeting (Kidding, there's some perfectly nice people there). But the point still stands -- social standing, zip code, parental achievement, and even height are all important factors in success; intelligence is only one facet of a successful individual.
This is, of course, assuming that we can freely increase intelligence with no repercussions -- are these high IQ individuals at risk of [schizophrenia](http://www.schizophrenia.com/sznews/archives/000607.html), or other mental disease?
I would also like to point out that the biggest real gains will come to those who move first. You can't be 5 sigma out when everyone else has the same gene modifications as you.