The real risk is that a contagion effect could bring about the split up of the Eurozone, and in that case a new Deutsche Mark would make German export much less competitive (and Berlin much less cheap). It's not likely, but it's still a big risk.
Which would rapidly approach equivalence to a New Deutschemark.
Germany has itself in the Euro trap just as strongly as the PIIGS. If they go under, how will Germany keep its currency down and where will it export to?
I agree that it would be an apocalyptic scenario and would require a lot of things to go wrong. But if every eurozone member only thinks about its immediate interests instead of working together and acting in a decisive manner, everything could really go wrong.
