I could see Obama coming in as a VP candidate in '08. He’ll play a good John Edwards - the charisma of the group, the spokesman. But by the '08 election, he won’t have the political experience to convince the voters he should be running the country. Perhaps after four to eight years of being Vice President, but not before then.
On a personal note, I’d love to the Democratic party’s most energizing and unifying spokesman since Clinton leading the party.