I think, long-term, the emphasis on colonization by European powers shall shift away from the Americas, and towards Africa, the East Indies, India, and Australia.
Already, the United States and Haiti have broken away from their former colonial masters, and Spain is having increasing difficulty holding onto its colonies, especially with what the French are doing to their motherland. Portugal may also see either a separation of Brazil or perhaps Brazil dominating the two. Spain, perhaps the greatest of the world's powers at one point, is done as a major power. Even if Britain loses its entire American colonial network to independence movements and US expansionism, they will still be a great colonial power through their effective dominion over most of India and Australia, as well as African and Pacific ports.
I expect an increasing amount of republican/democratic sentiment through the world. While the French revolution hasn't done too much for liberty (though, bad as Napoleon may be, his 'enlightened despotism' is a bit better than the old Bourbons), both revolutionary and evolutionary developments will see more limited monarchs and republican movements. British politics is far from immune to this, though outright revolution is unlikely; I expect substantial evolutionary reforms in coming years - Catholic emancipation, perhaps.
Probably the 3 biggest powers in the next few decades will be Britain, France, and Russia. Beyond that, who knows... China? the United States? Portu-Brazil? Great Republic of New Granada? Hapsburg resurgance? Sweden? Who knows...