Concerning Vettel, i think he will be eaten alive next year; no matter how fast the redbull is.
Vettel is a little boy compared to the likes of shumacher, Alonso, Massa, Hamilton and even Button, especially if they are in competitive cars. His delicate racing style will have him chewed up and spit out at the front.
He would have to be on poll and running scared to avoid confrontation, i can see why his odds aren't in the top of the top mix.
That redbull better be 3/4 of a second faster per lap if he wants to even be on the podium.

Webber stands a better chance since he knows how to dogfight even though he is slower.