I'd be surprised if Vettel doesn't become the WDC this year. He has everything working on his favours. Tracks that the Red Bull has always been good at and not to forget how brilliant and utterly dominant he was in all the circuits we have left to go to. On the other hand, I feel sorry for Alonso. He has been the best driver on the grid this year and Lewis comes 2nd in that respect but neither of them can win it this year. It has to be Vettel for all the bookies unless Ferrari gives Alonso a far better car or Hamilton really ups his game and wins 3 out of the remaining 5 races.
The difference between Alonso and Vettel and Hamilton has been the amount of PR about the car being slow that both Ferrari and FA have done. That and Ferrari's better performance under wet conditions have resulted in FA being overrated this year vs. Vettel and Hamilton.