I don't know how bitcoin will join the bank, but state banks will not join bitcoin and cryptocurrencies in general. Banks have completely different ways of functioning and making money. Cryptocurrency is by nature foreign to banks. Even if you don't pay attention to it, then banks will not risk enough to work with a cryptocurrency that has such high price volatility. Banks can exchange cryptocurrencies for fiat, where the risk for them is minimal. They can perform some other simple operations, but no more. They will use their own CBDCs in their work.