There seems to be a belief that the post-war 20th century order would be a fixed feature rather than a contingency of history. That the US would be #1, Europe #2, and the rest of the world would remain "developing" in rural poverty forever. That somehow China could be prevented from catching up. Now they are, and behind them India. I think people are going to be even more surprised in the latter half of the 21st century when South America and Africa start catching up as well.

Brazil is one to watch if they manage to achieve political stability, as is Nigeria if it can transition from being a petrostate.

And the end started when China was admitted to the WTO. They had this huge cheap labor force, a government that could centrally plan (in addition to ignoring little things like environmentalism or rights), and an immense wealth of resources. It was like a bunch of sheep letting a baby wolf into the barn. Now the wolf's all grown up.