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.
I think its eating more into the payment processors profits than banks (paypal, visa, etc). Plus the user base is SO small compared to those using traditional banks, I think they are relatively un-alarmed, but its
definitely on their radar.
I dont expect banks to really try and attack btc until the userbase grows
tremendously, and if they really wanted to attack btc, they could do so easily and severely, they have more than enough resources to do so