It will not be over. Hillary loves power too much, she will either keep her seat in New York and move to the left and become a muck racker (like Babs Boxer) or listen to me here, yes a Supreme Court nominee from an Obama administration. Think about it, she would love to sit on a life time appointment legislating from the bench as much as she could.
The failure to even get the nomination will be devastating to her and she'll have an absolute meltdown if and when that happens - mark my words. Now if she is somehow able to pull out the nomination and loses in November, she'll hang on to that senate seat for another chance in 2012. But if she doesn't win the nomination and the realization sets in that she won't have a chance at the brass ring again, look for her senate "career" to come to an end as soon as she can manage it.