The thing is, empires can take a long time to fall. Rome emerged as an empire around 30 BC and reached its peak shortly after 100 AD. It took another three hundred years after that for the empire to collapse.

The fall of the British Empire transpired more quickly, peaking after World War 1 and crumbling with World War 2, a span of only a quarter century.

There needs to be a new empire to fill the void. It looks like China or Russia may have those aspirations. But they still have a long way to go to position themselves.