didnt hear of any bank accepting Bitcoin yet.
That is not gonna happen because they have their own money, they only accept what is legal and regulated by the government.
Bitcoin as a currency cannot be regulated as banks cannot control, it will always stay decentralized and even if banks will create their own blockchain it will not beat bitcoin.
i don't think it even makes sense to have a bank keep your bitcoins, it;'s just like leaving your personal bank in the care of another bank and hoping it will be safe, why didn't you open an account with them then than setting up your own bank?
If you are going to compare bank and bitcoin, They are both increasing in value periodically and its not necessary to keep your bitcoins in the bank because the market is increasing the value its self.