Having one group of people outpace another group of people is only a bad consequence when you compare the two groups. What do the world's poor care if Westerners start altering themselves? Or is there going to be some tiered pricing system where $100k gets you an improved embryo but $1M gets you Superkid, so the middle class's Little Johnny can't compete with the princelings? That's actually.. pretty damn silly. And unimaginably unethical.
But it's just so utterly selfish to go "There's no way that rich kid can be made a genius! Everyone else won't be able to compete!" Really? Okay, so they can't compete.. and? He might discover a final cure for HIV.
A failure state would be what? Nothing actually happens? Okay, it didn't do what we wanted it to. We've learned something in the attempt and we've wasted more on worse ends. Maybe having the modified, corrupted-absolutely super-elite break out their maniacal laughter, go "lol noobs", and exterminate everyone else with as many infectious diseases as they could whip up? Mmm, smell that fresh omnicide. I'll be over here listening to the Gerry the Germ .SID.
Okay, back to reality. Human genetic improvement, if it's worth the name, means that some people end up genetically better than others, at least for a while, despite efforts to mitigate it. Which is the way things are already. We just won't be able to pretend anymore.