It's not exactly the same situation posed in your question and may not even apply to you (depending on how long you plan to stay in Korea in the future and how quickly you are able to get a new visa), but just be careful if your debit card expires while you no longer have an ARC or a work/student visa. Your bank account will still be open (it will close after 4-5 years of no bank activity such as deposits, withdrawals, etc.), but if your debit card expires in the meantime while you are without an ARC, the banks will not issue you a new debit card (a friend of mine experienced this/learned this the hard way recently).
One way to avoid this potential problem is to get a cash card that allows you to use ATMs (for things like deposits, withdrawals, transfers, etc.), since cash cards don't have an expiration date, so it will allow you to access your bank account as long as your bank account still remains open. A debit card, on the other hands, has an expiration date, so after it expires and if you are without an ARC at that time, the banks will refuse to issue you a new debit card (or even a cash card at that time). So it might be wise to get a cash card while you still have an ARC, just in case, to ensure that you'll be able to access your bank account without having to worry about an expiration date or being visa-less. Just a tip.