We all retire and let the computers run the economy for us, and devote our lives to the pursuit of happiness, art, love and other non-practical endeavours.
And when the computers start caring about art too, they'll join us, no doubt.
I really hope your vision comes true - I spend too much time thinking that computers are actually going to end-up as the Romans - we'll be their slaves... (pets?)
Mind you, there's another alternative, even more depressing than the one you mention:
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.
And when the computers start caring about art too, they'll join us, no doubt.