She says that she won't run for president again. Doug Mataconis accepts this at face value:

Hillary Clinton will not run against Barack Obama in 2012, anyone who believes she will is simply ignoring reality, and she will be 69 years old when Election Day 2016 rolls around. Would she be willing to put all her energy into what is likely to be a wide open race regardless of what happens to Barack Obama in 2012? I tend to believe her when she says she’s done.

Which is why, given her skillset and ambition, it would be foolish to under-estimate her potential to make a mark as secretary of state. But if she did have a successful two-term run as secretary - imagine if we did get a two-state solution, withdrawal from Iraq and Afghanistan, a reset with Russia and a Pacific/South Asian alliance to moderate Chinese ambition - I can see her being able to reconsider. 69 is younger than McCain was in 2008. And if my own feelings are in any way salient, my view of her has changed significantly given her professional and refreshing stint at State. I think she has won over many of her former foes.