I don't think there will be a sole superpower in the world like there has been since the collapse of the Soviet Union. There will be several key players such as the USA, European Union, India and China. I think Brazil, Russia and other countries such as Indonesia could be powers but to lesser extents to the others. Russia has the potential to reassert its self as a major power in the world, but it has such extreme levels of corruption and has failed to diversify its economy, I think I read that if you ignored the revenue from natural resources then Russia's economy would be smaller than Turkey. I also think a major problem for Brazil is the extreme poverty faced in the favellas, I don't think they can become a superpower with such extremes in wealth and the severe crim and drug problems that exist accros the favelas.
I can see the European Union emmerging from its current economic problems and growing stronger with further economic co-operation and possibly further expansion, while the individual countries probably would wield huge amounts of power, as a whole it would be very powerful in the future. The USA will still probably remain as a global power, although it does have huge debt and the rampant anti-Americanism across the world could cause their decline once alternatives to big American brands are developed by other countries. India and China will become more and more powerful with their huge work forces, China has already become a reigonal power across Asia a problem they face that not many people seem to talk about when discussing their future economy is the Chinese environment, it has been seriously decimated with the recent growth, land is becoming too power to grow crops and rivers and becomign heavily polluted, they have a huge population but that's no good if there industrial workers start suffering ill-health and malnutrition on a large scale.
I also think Africa as a whole will remain seriously underdeveloped, there is too much inner conflict, a lack of infrastrucutre and the brain drain of skilled workers and neo-colonialism by China will hinder any significant ecomonic progress.