wat happens if Anand wins the World Cup?

He will play both Topalov and Kramnik in matches.

but what then happens if he defeats both. wat sort of world championship match will be played in 2009 and who would Anand play?

He DID win the world cup. 

He will probably have to qualify to a tournament, then win it two times, beat a challenger, then beat Kramnik 3 times (4 if he is the challenger) and Topalov 5 times (6 if he is the challenger) or something like that I guess... ask FIDE.

Its a little complicated... We all know that 2008 chess champion will be decided by a match between Kramnik and Anand. However for 2009 chess championship the official rules are:

The World Chess Championship 2009 will be a match held during the first half of 2009 to determine a new World Chess Champion. The first, and possibly only, qualification stage will be the 2007 World Cup in Khanty-Mansiysk, Russia, held as a 128-player single-elimination tournament. Because of the special provisions for former undisputed World Champion Vladimir Kramnik and former FIDE World Champion Veselin Topalov, these players are excluded from the World Cup. All other top-rated players are qualified for it, including the current World Champion, Viswanathan Anand.^[1] There are two possible scenarios for the qualification process:

• If Anand wins both the 2007 World Cup and the World Chess Championship 2008 (against Kramnik), the World Chess Championship 2009 will be a match between Anand and Topalov.
• Otherwise, Topalov will face the World Cup winner in a match of 8 games during the second half of 2008, and the winner of that match will challenge the reigning World Champion in the World Chess Championship 2009.^[2]