Indeed; that's why I included the "don't need bitcoins" case(already have euros in hand) and the "won't be helped by bitcoins"(nominal euro holdings are frozen in a bank or similar, and are at risk; but also unavailable to buy bitcoins with.)
I definitely suspect that somebody is going to be taking quite a bath on this; either holders of Greek state debt, or Greeks with cash in easy reach of the state, or both; but I just don't see how bitcoins outperform 'in-hand' euros, or dollars in terms of weathering the transition; while anyone who can't get their euros is probably in deep shit; but can't buy bitcoins because they can't get to their euros, so they won't be helped much by bitcoins.
I definitely wouldn't want to have money stuck inside Greece should it exit; but barring all but the most heroic border controls, not a historical strong point of the Greek government, just walking the euros out if you have them will be relatively simple(and, if doing so is illegal, so would getting the same euros out-of-country by buying bitcoins from a non-greek, the money needs to move either way); while anyone who doesn't have them may well be stuck; but also doesn't have cash on hand to buy bitcoins.