The German government has been simulating a range of scenarios to prepare for a possible exit of Greece from the euro zone. Under a worst-worst-case scenario, the country could descend into a vicious circle of misery that could last decadesThe Greeks could see the type of inflation that Brazil saw for so many decades. 50% or 80% inflation. (Listen to Act 1, of The Invention of Money, for a description of what a worthless currency looks like. And how one country turned the situation around.)
If debts remain denominated in Euros, Greeks could be in big trouble, even if they reinstate the Drachma.