My guess is, Obama will be the candidate in 2016. If he loses this time he is still constitutionally eligible.
If he wins this time, they simply change the Constitution. by fiat if necessary. Or just ignore it like they did with that "natural born citizen" thingy.
If Obama wins this year, he can have Michelle run in 2016 (the was Lurleen Wallace ran when George Wallace was ineligible).
If Hillary doesn't run in 2016, Chelsea will be old enough to run instead. Being (legally) the daughter of Bill Clinton should more than compensate for lack of any policial excperience.
And the Kennedys will never run out of potential candidates...if Teddy could run for President after killing Mary Jo, RFK Jr. could run despite driving his soon-to-be ex-wife to suicide.