So I've just started reading a collection of Tony Judt essays that date from the mid 90s. It's very interesting to get his foresight on this issue. He predicted that as the EU expanded eastward and southward, that it would inevitably face an existential crisis. He basis this on the fact that even at that time, the only countries that provided more financial support to the EU than they received were Germany, Britain, France and the Netherlands (maybe one or two more, Belgium perhaps, don't have the book in front of me, but suffice it to say they were all from the north), while Spain, Italy, Greece, et al, were perennial charity cases. He asks how this can be sustained when the Soviet bloc is integrated, as was beginning to happen at that time. He goes on to predict that Germany, against its own better judgement, will become the hegemon in Europe once again. Quite prescient, although it turns out that current 1990s members are the calamitous ones, and not the bloc countries.

I think a direct coup is unlikely. It would be too obvious in this day and age, and it would be difficult to get most countries to recognize the new government. I think it's more likely that a shadow coup could take place, in which the European court somehow neutralizes any and all decisions made by the Greeks with regard to international finance. I think EU would prefer a castration to a beheading.