I don't think Hillary will be a presidential candidate again. If you seriously contest the nomination and lose, it's hard to get back in again. McCain did it, Reagan did it, but I think it takes a lot of changes in order for it to be possible. Of course, that's what Obama is gonna deliver so who knows.
Seriously though, if Obama wins the door is definitely closed. If Obama collapses completely we could see a "I-told-you-so" case from Hillary and if McCain does not run for reelection or maybe even more likely if he does, she could run in 2012. If Obama loses narrowly I don't think she'll have much of a chance either.
I do believe that she will stay in the senate, possibly for a long time. She enjoys politics.
