The Greek situation has no good ending, regardless of whether they stay in the Eurozone or not.
If there is even an inkling of Greece leaving the Euro, and inflating their new currency, then there will be a a major bank run on Euro cash in Greece before that happens. Greek govvie wont be able to bail its banks out (as its broke), and the banks will go bust, taking with them the savings of the Greek people. Suddenly, you don't just have a Greek sovereign debt problem, but a Greek bank debt problem. This will flow on to other Eurozone banks (that hold Greek bank debt), possibly causing bank runs europe-wide, not to mention a likely revolution in Greece.
- Euro fuc*ed
If the French/ECB plan goes ahaid, and Greek Govvie debt is 'voluntarily' rolled over, the situtation will be no better. Fitch Ratings has said that even a voluntary roll-over will be classified as a default event, trigerring the CDS's that have been written over Greek debt, as well as removing Greek bonds from the pool of collateral that can be posted with the ECB for overnight loans. Fitch and S&P have also said that the major French banks will likely be downgraded as they are large holders of Greek debt. Again, this will lead to a liquidity crunch, possible bank runs, unrest, etc...
The design of the Euro itself has led to this - permitting multiple fiscal policies to operate alongside a single monetary policy, not to mention that Greece was admitted to the European economic region (pre euro days) to counter Russian influence, means that short of Germany annexing Greece and fixing it up like East Germany, there is no happy ending to this.
Sources: yesterdays fin reveiw, bloomberg, the UBS credit desk, and my personal analysis
