Ferrari don’t seem particularly optimistic so far. You have to assume that Red Bull will produce a good car again, and that McLaren will be pretty close as well.
I don’t think Webber will ever beat Vettel, so I think it’s going to be between Button, Hamilton and Vettel, and Alonso if they can sort their car out soon enough.
I would love Schumacher or Raikkonen to be a contender, but I don’t see that happening yet. This is probably going to be Schumacher’s last year unless he can really improve on 2011.
I think Raikkonen’s got a serious chance of getting a second World Championship if he sticks around for long enough- but I don’t think it’ll be this year.