I don't see that the default is inevitable, because a default state is a state when a debtor cannot pay his debts to the lender. But what if the lender doesn't demand the payment? Then the default state can never occur. The west countries might not want to demand the debts because they can afford to lose some little money and get an important geopolitical ally, and Russia might wait with the debts in order to avoid a new confrontation with the west countries.