As of today, 80{c02dde72df927a7b1629fc29506cd3151b0442defda0d37a402db978ff19aaf8} of all Bitcoins that will ever exist have been mined. The next halving is a little over two years away, at which point inflation will fall to 2{c02dde72df927a7b1629fc29506cd3151b0442defda0d37a402db978ff19aaf8}. This means central banks can only get at most 20{c02dde72df927a7b1629fc29506cd3151b0442defda0d37a402db978ff19aaf8} of BTC supply. Unless you sell it to them for their fiat altcoin.