As I expected, NASA just announced that Ed Weiler will be the head of NASA's Science Mission Directorate for the duration. Weiler replaced Alan Stern, who stepped down a few months ago amid controversy over funding, budgets, and the Mars rovers. Weiler has a long history with NASA science and was the obvious choice for a temporary replacement for Stern, and it's not surprising at all that he has been asked to stay on.
Typically, when a new president takes office, Agency heads and such tender their resignation. The new President can then decide whether to accept it and replace them, or to deny it and let them stay on. Hard to say what will happen to Mike Griffin when a new President takes office in January 2009, and what will happen to the top spots at NASA. It's an interesting thing to ponder though. I've had both praise and vinegar for Griffin, and in many ways I'd like to see him stay on, though in other ways I wouldn't mind seeing him replaced. He has done a great job for NASA in many many ways, though all things being equal I'd be happier with someone who thinks global warming is real and a danger and isn't dismissive of those who disagree.
Probably more important is how a new Congress will treat NASA. So much to think about! It'll be very interesting to see how this plays out over the next seven or eight months.