I think the Greek debt stuff is not that fundamental to the world economy. Greece just isn't that big. Even the rest of the PIGS aren't THAT big.
I would expect sometime in the autumn. Actually, let me rephrase - if it DOESN'T happen in the autumn, we are in deep shit. We know that the Obama admin will do everything possible to create a rosy picture for the mid-terms. If they can't, well, uh oh.