Spain will win it. Objectively and subjectively, Spain have a very good chance of successfully defending their crown as current World Cup champions. The tournament is 3 years away, they have a young and very talented core group of players that will still be able to play in 2014. In addition, Spain are also the current U21 world champions and U19 European champions and the standouts from those squads will ensure that the conveyor belt of highly skilled players continues to provide the Spanish national team a deep pool to select from.
As hosts, Brazil will be extra motivated to win it so they will be favorites too. Argentina with the world's best player, Leo Messi, will likely relish the chance to spoil Brazil's party by winning the World Cup on Brazilian soil. Dear Lord, if that were to happen it would be shades of the trauma of 1950.