There are lots of betting markets and discussions flying about already as to who will play who in the latter stages of the 2010 World Cup.
For example, I was involved in a discussion the other day with someone who was convinced England would lose to Portugal in the quarter finals in South Africa. I was pretty sure I was right, and I checked my schedule to make sure. England can't actually meet Portugal in the quarter finals, irrespective of where the two finish in Group C and Group G respectively.
Similarly, assuming Germany and Spain win their respective groups (they should do) then they can't meet in the World Cup Final. And yet, it's a 22/1 chance that they will be the two finalists when it is 25/1 that Germany will meet Brazil in the Final, which is perfectly plausible based on the draw.
Anyway, the moral is this: do your research.
(my tip, for what it's worth, is Brazil v Italy at 22/1. And, if Brazil or Spain don't win their group, they'll meet as early as the last sixteen. Eeeek.)