Unless the Greeks themselves actively push for a way out of the EU there is no way it will happen. The Troika and other Greek creditors have already tacitly admitted that they don't expect to get the full value of the debt back and pushing Greece out of the Eurozone and back into a Drachma that would float on the markets would massively inflate the value of the debt from a Greek perspective. The chances of any serious amount of debt repayment would then disappear. All the talk of the ECB refusing to lend to the Greek banks or Greece being shut out of the capital markets is just neoliberal rhetoric and bullshit. If any of those things actually happened, the country could fairly quickly descend into anarchy and destabilise the entire region. History suggest that this type of disruption near the Balkans is unlikely to be sanctioned.
The upshot is that Syriza probably has more power and leeway here than the popular press would like to admit. It all hinges though on whether Syria can stay in power long enough to start acting on its manifesto or whether spin from the Troika/press/markets etc will destabilise its government and replace it with a party more likely to play the austerity game. You can be sure that the major capitalist players all over the world are working round the clock to make this happen. But in the meantime Greece aren't likely to be kicked out of the single currency.
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