If Greece goes the Euro goes. (Actually if any Eurozone country goes the Euro goes).
I believe that the Greeks are overplaying their hand here. A few years ago, this might have been true, but now, international financial institutions have had time to prepare for the "Grexit" as a seriously possibility and create contingency plans.
Greece is less than 2% of the Eurozone economy. If Frace, Spain or Italy jumped . . . then they would have a problem. The Euro will survive a "Grexit", and be probably come out stronger, because the world financial markets will see the Eurozone as an organization that will not tolerate financial "fudge." And that the Eurozone is committed to keep the Euro a "hard" currency.
Let's face it . . . why are the Greeks in the EU anyway? They aren't really European . . . they sit at the butt-end of the Balkans, as one English diplomat put it, "half Byzantine, half Turkish by temperament." And why are the Turks in NATO? Turkey . . . and North Atlantic?
Well, if we take a look at a map, we'll see that Greece and Turkey together control the strategic Bosporus and Dardanelles Straits. These were important during the Cold War, when the EU and the USA were fearful of the Tartar hordes of the USSR sailing through. This is the only reason that the EU wanted them in.
After World War II, the Greeks were very close to flipping over to Communism. Well, the voters of Greece have now done it. I worked with a couple of guys from Greece a few years ago. They voted early, and voted with their feet. One works in Ireland now, the other in Spain.
Plus Greece cannot be kicked out of the Eurozone by anyone. Actually there isn't a provision for such a thing in the treaties that implement the Eurozone.
Just do a search on Google news on "Grexit". You will learn how this can happen:
http://www.ft.com/cms/s/0/8fd55736-ae0a-11e4-919e-00144feab7de.html