Wrong. The way it appears now, the debt is going to be repaid over a longer period of time. Your confusion about this indicates that writers are not doing a good job explaining this to people.
But the existing bonds still have value and they'll still be held as investments. It's not like the whole country has collapsed and the value of its debt is worthless. A haircut is just that, a downward adjustment in the value of the debt.
It's inane to think that Greece will exit the Euro zone because of this. The Euro zone is the only thing keeping them going at this point.
Debtors have "an option" to gain additional guarantees at an additional cost. For debtors that don't enter into such additional contracts, Greece made all the payments up to date.