Who thinks there will be four major Union's in the World, each will issue a digital currency?
So the question is more about the four main unions, the digital currency is an sub question I guess.
Who are these four main unions? I see no formation of any unions apart from the EU. The EU isn't really setting the best example of why we should make these unions either.
Anyway, I see a future where all countries are going to race to acquire as much bitcoin as possible and even create sidechains based on their own needs and use.