I believe that Obama doesn't want to be president as much be an ex-president. I think he is much more enthralled with the following he would attract speechifying with the gravitas of having been the president than he is with the burdens of having to make decisions. He is much more comfortable in the rhetorical world of strawmen and sonorous platitudes than in the real-world where facts often vitiate the pleasant-sounding theories and aspirations of his speeches.
I suspect that Obama will come to the same conclusion that Palin did: that responsibility is limiting, and that political genius and divine insight can be frustrated by the tether of executive responsibilities. Deep down, I doubt that Obama has much ambition to be remembered for the nuts and bolts of his managerial responsibilities, but instead yearns to be a transcendent figure, lecturing across time and continents. In short, I suspect that Obama knows knows that his influence is limited by the day-to-day responsibilities, because the hard decisions he has to make will give lie to the vaporous but seductive ideals that he would rather talk about.