What I think is likely to happen is that there will be a primary and that Hilary will be in it along with Joe Biden. I don't really know who else would jump in. I really don't think Biden would have a chance against Hilary.
There is a second scenario that is unlikely. Obama could run for a third term if the constitution was amended to allow it.
As for the general election, I really believe if the republicans nominate a true fiscal conservative/social moderate with balls (male or female) and the ability to communicate the conservative fiscal position, they could win against anyone, even Hilary. Having said that, yes, Hilary will be the next President.