I highly doubt after being President of the USA that Obama would want to be vice president or be back in that environment.
but..
"However, the wording of the 22nd Amendment doesn’t literally say that no one can be President for more than two terms; only that no one can be elected President more than twice
Presumably this still leaves open the loophole (intended or not) that one who had already been elected twice could still serve as President again by attaining that office through other means — particularly, by being elected or appointed Vice-President and thus becoming next in the line of presidential succession when the sitting President dies, becomes incapacitated, or resigns"
"No person shall be elected to the office of the President more than twice, and no person who has held the office of President, or acted as President, for more than two years of a term to which some other person was elected President shall be elected to the office of the President more than once."