I'd wait to see the 23-man squad lists first. Managers have screwed many teams because of their stupid choices of tactics and players/
Brazil are the big favourites, they can call up 5 competitive teams at the same time and everyone could be considered as a contender. However, this Brazilian team is not as sparkling and flashy as it was in previous years with Ronaldo, Rivaldo, R Carlos generation or that one of Romario, Bebeto and Mauro Silva.They have Kaka, the always-underrated Fabiano, Bastos, Maicon, J. Cesar, Alves...good gk, experienced defence, creative midfield and a performing striker. So Brazil are the big usual suspects.
Argentina should be written off, right now only the talent of certain players could save Maradona's tactical unawareness. Same goes for Domenek and France. It's a shame, Argentina and France have such a great generation of players, but a ship without good skipper can easily be sunk by the underwater stones.
Italy and Germany are teams with great traditions, despite being unimpressive in their WQ campaigns they can reach the later stages and beat everyone. I don't think that Italy stands any chance of winning the cup again, they past it, Lippi will do great if brings younger players with him. Germany should never be underestimated even though they don't have superstars like before (the times of Klinsmann, Matthaus, Voller etc).
This is the last chance of a very strong English team to do well. This could be the last appearance of players like Terry, Ferdinand, Lampard, Gerrard, Barry, Beckham at the world cup and this team is as strong as that of Italy'90. I believe they can make it to the semis.
Spain have the best players, I don't think that any other team (even Brazil or Argentina) can offer a better or more creative midfield. Xavi, Xabi, Iniesta, Senna, Silva, Mata, Fabregas, maybe Caneles, Granero - Del Bosqe will get a headache before naming his starting line-up.
African teams will do well, I can see at least two teams making it to the last 8.