Not that into looking into the past for figuring out the future, but if you are going to use the pre WWI period as a template you should note one interesting fact. Namely, there were two rising powers - Germany and the US. One chose to take on the hegemon, the other allied itself with it against the other rising power. So playing your WWIII = WWI scenario - US = Britain, EU = France, China = Germany, Russia = Austria-Hungary, ? = the US (India perhaps?).