I don't think it is clear that an exit would forestall a re-run any better than their already ruined credibility .

(another way to look at it: the interesting question on the table is how much of their existing debt the Greeks are going to repay, future debts aren't going to be a serious problem in the short term regardless of what happens)

I also (while not thinking my opinion is worth much) think that the economic damage from an exit would likely not be worth the ability to self determine further ruinous fiscal policies.