If the diffusers are legal, I think Button has the best chance. But there are a lot of candidates, so even then I wouldn't put Button's chances as being more than about 30%.
If the diffusers are illegal, I'd think that Massa has the best chance. But again, he's one of many possibles.
I don't agree. I still think there will be a gap between the former-diffuser teams and those that didn't have them, should they be declared illegal, although it would then make it much easier for the other teams to close the gap. Of the non-diffuser teams, I'd give the Red Bull drivers the best chance, to be honest. As long as they cut out the mistakes, that is.

Seems like a lot of people are posting after hitting the crack pipe tonight. 
It's allll good stuff, maaaaaaaannn. 
On a more serious note, I think that Mika Hakkinen will come back to replace the out-going Lewis Hamilton, miraculously find the speed that he (sadly) seemed to have lost, and blitz the entire field. Frustrated at Kimi Raikkonen, Ferrari will sack him, leaving the seat open for Michael Schumacher. Next season it will be another Schumacher-Hakkinen classic battle and Formula One will move away from the scandals and nonsense of the modern era and go back to the good days.

I want some of what you've been smoking... 
It's widely available
