I don't agree that Fong would necessarily win reelection in 2004. His Democratic challenger would probably benefit from pretty significant coattails from the Democratic nominee for President that year (possibly Gore running for reelection?). Also, he suffered from cancer in 2007, meaning he would have a hard time campaigning for the Presidency in 2008. Of course, there are other considerations we need to take into account that don't directly involve Fong. Is the President (perhaps Dean, Kerry, or someone of that sort) running for reelection in 2008? Is the incumbent President serving his second term (perhaps Gore, Bush, or McCain)?
All that aside, I don't think that Fong would be likely to win the nomination in 2008, and winning the presidency is even less likely. He doesn't seem particularly remarkable (though this could be different ITTL), and just being a skilled State Treasurer/businessman isn't enough to break out in the crowded 2008 field.