He's already cooked his own goose then.
You're correct that the governor's mansion is a better launch point for a run for President. I believe the common wisdom holds that a governorship is a comparable position to the Presidency, and equals a kind of promotion in the ranks, rather like promoting an office manager to the board room. Yet governors have plenty of baggage as well, if they've served long enough to accumulate it.
If a Democrat wins the White House, Obama could hope for a high visibility cabinet post. It would get him into the Executive branch, and get his face in the public eye. That is, if he's any good at administrative work. I still say he's too green for the highest office in the land.