what happens if bitcoin builds a bank just like a bank with a headquarters, savings account management and also makes a bitcoin account card ??
bitcoin is not a person to build a bank.
bitcoin is not a centralized group that can build a bank.
anything that is made is made by third parties like you and me.
nothing happens when others offer different services such as wallets (coinbase, xapo,...) exchanges (bitfinex, poloniex,...) gambling sites (....). so nothing will happen when someone offers a "bank" services too.
what did you expect to happen anyways?