When EU actually fails, we can say that it failed, till then all such predictions are hot air.
I see that some people do not like the idea of Unions, may be its because they have a big country and they do not want others to have big unions of states like EU, it is only natural, because the bully's will then no longer be able to continue bullying.
The idea of unions is to stop migration, because when there is economic opportunity within country there is no need to migrate for jobs. And Bangladesh has much more land per capita than Singapore or Hong Kong to house its future population and set up the industries to employ them. Land shortage is not why people migrate, it is because of lack of economic opportunities.