One day banks will accept Bitcoin as medium of exchange and accept deposits from bitcoiners. As soon as the world powers accept it as medium of exchange.
I think it will take about a decade for banks to start having a large amount of bitcoin as reserves.
The "central bank of central banks" already allowed central banks to have up to 2% of their reserves in bitcoin.
That's a massive change in how banks work, and I can assume this will only expand over time.