I don't see germany coming. We have had our share of world power and it didn't go very well. We are also way to small and don't have the military to support a claim for a legitimate superpower. We have a strong economy, but that won't be enough, as we also have quite high unemployment, and our economy is not growing much.
china is a superpower already, at least as their economy is concerned. They have mostly stayed out of the later conflicts (afghanistan, iraq, war on terror ). But sooner or later, they will engage, as soon as their security interests are threatened. But I don't know what that will take, as they are pretty much predominant in Asia already. Terrorists seem to shy away from China. So as long as no one threatens their national security, I don't see them engaging in any military action. and really, who has the power to threaten China ? No one...
So they will be moving along, quietly taking over the world economically.
North corea ? na, forget about them. rethoric, that's all. They don't have the economy to make legitimate claim.
India is a possible candidate for the future. Huge economic potential, very open society, dedicated workforce.
russia is going down, and is probably at no. 3 right now.
my personal ranking would be:
1. USA
2. China
3. Russia
4. India
5. UK / France / Germany
Pos. 4 and 5 are kinda interchangeable, as there are currently only three real superpowers. The rest has some influence, but only regionally. I believe that USA and China might change positions in the future, but that will depend largely on any possible involvement of china in an upcoming regional conflict.