My feeling is that slowly but surely the rest of the world is catching up to the european/south american powerhouses, and results at upcoming world cups will reflect this growing parity. Not to say that there arent perennial favorites, just that perennial results will be harder and harder to come by.
Having said that, my top 4 at this time are:
1. Serbia & Montenegro
2. Argentina
3. Brazil
4. Croatia
My Dark(er) horses: Paraguay, Costa Rica, Sweden, Mexico