I've been expecting Hillary Clinton to run in '08 since the late 90's. So I'd say Hillary for the Democrats.
For the Republicans...you never know. If Hillary is the Democrats' candidate, the Republicans might (MIGHT) put up Condileeza Rice. But there really aren't too many people the Republicans have so far that have enough of a record or background or are widely known enough to consider a run for the Presidency. Of course, that's more than three and a half years away, so there's plenty of time.
