What the fuck are you talking about?
Banks in no way can centralize Bitcoin. Purely hypothetically they might accumulate enough bitcoins which could be loosely interpreted as a sort of centralization, but this is hardly ever possible given that Bitcoin superwhales don't look as if they were going to part with their stashes soon. Other than that, no one forces you to use Bitcoin bank services should such services appear in the future
Ofcourse no one can force someone to use a bank for storing their bitcoins as long as everyone has their own coins stored in their own wallets, because bitcoins gives us a financial freedom which means we are our own banks, so even if the concept of bank comes into being, we are still the owner of our choices.