In this current week (from 12 May 2014) the favourites to win, by a long way are the home team - Brazil. At the moment the odds are at 3 to 1 for them to win. After that the next favourites are Argentina at 9/2, followed by Germany with odd of 11/2. Spain and Belgium are also possible if unlikely winners, with Spain currently at 13/2 and Belgium a long way behind them at 14 to 1.
A lot of the high expectations for Brazil are based on their strong performance in 2013 in the Confederations Cup, when they beat Spain who were the previous champions. Being the host team can also bring a big advantage - and some have pointed out that being used to the hot Brazilian climate will also help. However, the World Cup of course is another matter and nobody is pretending to be sure of who can win.
You can see the latest odds here.