I'd be surprised if Biden got the nomination. He just doesn't have the gravitas or the charisma, IMO.
Hillary, on the other hand, would be much less surprising. It's impressive how much her favorability ratings have improved; she used to be a very polarizing figure, but now her poll numbers
are 56% positive against only 25% negative.
But there'll be a lot of water under the bridge between now and 2016. As they say, anything can happen — and it probably will.