obviously a good deal will happen between now and then.
The good thing is that the handful of seats listed as toss-ups by Charlie Cook are all currently held by Repugs: the retiring Mel Martinez (FL), sorta crazy Jim Bunning (KY), and David "Diapers" Vitter (LA). We saw FL move in a blue direction in '08, after that backslide in '04, which is good news. It's scary that KY reelected Bunning in '04 after the "getting beaten by little green doctors" comment and assorted other weirdness, but Bush will not be on the ballot in 2010 (although KY isn't exactly moving in a "D" direction.) LA is one of the few states that actually became redder in '08, and may be more forgiving than many other state's voters would be about Vitter's fetishes, but if we can get a strong candidate Vitter is at least more vulnerable than he would have been otherwise.
http://www.cookpolitical.com/charts/senate/raceratings_2008-11-14_09-22-07.php