Will never happen, there's far too many selfish smart people who aren't waiting to have kids. There will be a ruling class as long as we continue on this path.
I mean, I'm not saying things can't get better... but they'll never be like Idiocracy. The reason people seem to be getting stupider isn't because of eugenics, it's because of the concerted efforts of those in power to stigmatize intelligence. They're not just going to up and disappear... they're going to exploit the under-educated.