I highly doubt there would be a bank for bitcoins because the whole point of btc is for it to be anonymous and that bank will totally destroy that ideal.
Indeed, you are right! All banks are centralized or regulated industry while bitcoin is not centralized. although bitcoin for some other banks butcoin for them is a threat to their business. But the reality is not, instead bitcoin is very open type of source to any business.
I don't think there is any bank at a moment that is accepting bitcoins and even I don't see it happening even in future as bitcoin is a competitor to the banks so I don't think that banks will ever stand in support of bitcoins or will start accepting it.
To be honest, bitcoins in banks as a payment is possible just like in Japan that they already accepted bitcoin to their country and that means that there is a possibility for bitcoin to be accepted in banks as another type of payment, If a country or government accept bitcoin then its authorities will follow from its decisions.
I dont think things are that easy the fact a payment method becomes accepted does not mean that a bank needs to adopt it, they may choose not to do it, with lame excuses like saying that criminals use bitcoin and that they refuse to accept it or something like that.
Japan accepting bitcoin is just a start. all speculators and researchers will be watching bitcoin closely. if by any chance its unable to meet their
desired results. it can always fluke. since this is just starting point. the changes are still not that huge but hopefully as it go on and proved to be
successful we can actually see some changes. read the report of nomura research institute. it says bank acts and other laws may needed to be
changed if we want to adopt this technology