Bitcoin is a threat to them for sure but I don't think they have to be worried yet as it's going to take quite some time before bitcoin starts to eat into their profits but I hope its sooner rather than later. I think people are always going to need banks though but bitcoin will likely flourish in parts of the world where people do not have access to a bank.
Yes it is a blessing for those who don't have bank accounts, it would surely attract them towards bitcoins, and as of today we even don't need credit cards for online purchases as bitcoin is taking care of that too, so it would surely affect the business of banks.