There is also the open question of the ultimate disposition of Europe's growing Muslim population, most of whom, as far as I can tell, live in virtual ethnic ghettos (Germany) or real, filthy disgusting ones (France) where they are both feared and despised. How and whether the Europeans can integrate such a dissimilar population into the existing Volk is an interesting question.
As for Russia, Putin is willing for the moment to appear to be all things to all men: helping us in Afghanistan while siding with the Europeans diplomatically in Iraqand selling massive quantities of weaponry to the Chinese to pay for Russia's own debilitated armed forces. Russia should become a very wealthy country in a generation or so, given both her enormous natural resources and her well educated population. But even that is somewhat in doubt given her political history of squandered opportunities. Right now she can barely hold herself together, and her attempts to reassert an imperial presence in Central Asia or Bielorussia, Moldova, etc., may backfire badly. And, ultimately, as Putin must realize, China is the only potentially serious security threat (besides Islamofascism) that Russia will face.
As for China, I'm actually optimistic that as material conditions and education improve, the Chinese people will themselves demand more accountability from their own government. The Chinese, while fiercely nationalistic, are not idiots (unlike the Arabs). But this will be gradual, with the big change coming when most Chinese can no longer accept the threat of violence to maintain a one-party state. It will simply become too face-losing to try force when the majority will no longer accept the bald face lies of the Communist Party. China will also face a major retiree problem exacerbated by its one-child policy in the next 50 years.
All bets are off, however, if there's a big economic meltdown, which causes Beijing to try to seize Taiwan a la Galtieri in the Falklands.
What about the US? By the end of the century, the US should reach population parity with China and India. And we have a lot more options to play than most others, including the one telling the rest of the world to kiss off and withdrawing behind our Pacific and Atlantic moats if we choose. A lot will depend on whether we get nuked by the Islamofascists, or whether the current struggle turns into an all out war between the US and the Arab/Muslim world.
My best guess is we'll muddle through, with our current preeminence somewhat diminished but still quite high.
If one looks at the balance of economic power in Asia, there are three main foci: India, China, and a historically anomalous axis running from Taiwan through Japan to South Korea. The latter two hate each other's guts in theory but all three are more or less liberal democracies and wealthy to boot. Nor are they fools. They know perfectly well that China considers them potential puppets, an attitude stretching over a thousand years of futility and illusion. To outsiders it may appear the Asians versus the white foreign devils; in fact, it is anything but.
Old Europe is a combination of theme park and retirement home, and it still fancies it's in charge. Everyone it listens to thinks so, principally because it only listens to itself. Russia is in a race between economic renescence and demographic catastrophe. New Europe is finding out that it is strong, and is scratching its collective head at the quaint notion that the French are driving. Whither? Why, in circles around Paris, of course - doesn't the whole world? What they are trying to build militarily at the moment is a cheap union army commanded by bureaucrats. There is nothing in the world that is both cheap and union, and command by bureaucrats is a notion too horrible for any military man to contemplate.
The Americas are two continents, not one. That they will remain. Despite decades of exploitation propaganda to the contrary, the South really doesn't have anything the North covets and the North will, at some point, tire of the neighbors moving into the rec room and begin to conrol immigration once more.
In short, a mess it is, a mess it always has been, and if it ever becomes anything other than a mess it will be because we're all dead. Seeding the world with a number of relatively independent, noisy, contentious elective governments is the best guarantee against the sort of monolithic zombie march Orwell predicted in 1984. That may be one reason we're trying it.