Throughout evolution, no species has ever permanently dominated the top of the food chain; it always gets replaced by something else. There's little reason to think that won't happen to us too.
The best I can do is think of Rome's slave based economy. Obviously slaves can do anything the free Romans could, and they did. The Romans were either plebes, dependent on government handouts like bread and circuses, or they were wealthy and then they mostly went into politics.
Most of 'em were working in the fields, most of the rest were serving in their masters' houses, and the majority of the rest were probably doing far worse things (working in the mines or dying as gladiators).
http://www.amazon.com/Artisan-Workers-Upper-South-Petersburg...
And when the computers start caring about art too, they'll join us, no doubt.
90% of the human population finds it impossible to transition to a life of plenty, where there's nothing to do other than enjoy yourself and/or pursue abstract notions, and so a great world war emerges, destroying everything that we've spent a million years of evolution to achieve, and ending humanity's brief reign on this planet.