The 20th century was marked by a stand-off between two factions: totalitarianism and democracy. The totalitarians, of course, were the Nazis, the Communists, and various smaller fascist and socialist wannabes. The democratics were the United States, the British Empire, and their allies.
I suspect that the 21st century will be marked by a similar stand-off, but this one will be between expansionist Islam vs. Everybody Else. How this will play out will depend on a number of factors: the capability of Muslim countries to acquire weapons of mass destruction, the shrinking birth rates and moral disintegration in Western nations, the possibility of major natural disasters such as volcanic activity or changing climactic or environmental conditions...and by extension, water shortages, oil shortages, famine, etc., and the possibility of the collapse of global economies.
No matter how it all cooks down, by the time 2100 rolls around, things are likely to look a lot different than they do now. Hopefully, Islam will either be contained to its own areas, or will somehow learn to live with the rest of the world. Or maybe Jesus will return---which, let's face it, would be a good thing, at least for those trying to live for Him.