How likely is the formation of the United States of Europe?

It has been put out there that the only two ways out of the “Euro Crisis” are kicking out the weaklings (Greece, Spain, etc.) or a complete political union in addition to the currency union.
The fact is that Greece and Co. do not have the necessary economic strength to have a strong currency such as the Euro, so they have to either leave the currency union, to have a currency befitting their economy, or become part of a political union, to align the political and social systems necessary to uplift their economy, so that they can afford to have the Euro.

I do prefer the political union, but how likely do you think it is that this will happen, and would you be in favour of that?