Most tournaments see the bulk of the same countries qualifying from each continent. Iraq are the Asian champions, and their opening 1 - 1 draw with China in the Asian group stage qualifier was quite promising. Haiti won last year's Caribbean cup, but I can't really see them finishing above the likes of Mexico, USA and Costa Rica.
I think the qualifiers themselves are where to look for upcoming nations. There is improvement in the Caribbean, with minnows like Turks & Caicos, Bahamas and Belize all showing graet improvement in recent years. However, encouraging results in the early qualifiers, won't mean qualification.
Africa have a wide ranging array of talented national teams, and they all seem capable of beating each other, especially at home. The 2006 saw four of the five African qualifiers make their debut at the Finals, so maybe if there is to be a shock qualifier for the finals, it will once again come from Africa. Mali, Sudan and Botswana are all improving rapidly.
Personally I think the most likely "newcomer" to the World Cup Finals will come from Europe, and will be in the shape of Serbia, who would be competing in their own right for the first time.