Just taking a look at the points; in case anyone's interested;
Vettel 234
Webber 149
Hamilton 146
Alonso 145
Button 134
Right now there are 200 points to play so it's still very open. It's not possible for Vettel to wrap things up by Monza either. The earliest possibility is Singapore (race 14, 5 races left, 125 to play for). Do note that in all of my calculations I put him up has having clinched the title by 1 point at least; and I don't take into account countback as there are more races left than Vettel has already won this season.
In order for Vettel to wrap things up by the Singapore race chequered flag; he has to, over the next 3 races, outscore:
Webber by 41 points (13.67 average)
Hamilton by 38 points (12.67 average)
Alonso by 37 points (12.33 average)
Button by 26 points (8.66 average)
For him to do so by the Suzuka chequered, he has to outscore (over the next 4 races):
Webber by 16 points (4 average)
Hamilton by 13 points (3.25 average)
Alonso by 12 points (3 average)
Button by 1 point (0.25 average)
By Korea, it changes the picture dramatically, as Vettel just needs to "not lose" points rather than "gain points."
Webber can catch him by 9 points (1.8 average)
Hamilton can catch him by 12 points (2.4 average)
Alonso can catch him by 13 points (2.6 average)
Button can catch him by 24 points (4.8 average)
By India:
Webber can catch him by 34 points (5.67 average)
Hamilton can catch him by 37 points (6.17 average)
Alonso can catch him by 38 points (6.33 average)
Button can catch him by 49 points (8.17 average)
By Abu Dhabi:
Webber can catch him by 59 points (8.43 average)
Hamilton can catch him by 62 points (8.86 average)
Alonso can catch him by 63 points (9 average)
Button can catch him by 74 points (10.57 average)
By Brazil:
Webber can catch him by 84 points (10.5 average)
Hamilton can catch him by 87 points (10.875 average)
Alonso can catch him by 88 points (11 average)
Button can catch him by 99 points (12.375 average)
Now I hope I haven't scared anyone off here; and that you all understand the numbers. Cya in 4 weeks guys