let's say we're 20 years in the future and the world has adopted bitcoin as a global currency. We develop very sophisticated processing technology, and a bunch of nerds hack all the secret keys of the bitcoin network. That is a bad future.
Well as you said that it is in the future sophisticated firewalls and security will hinder bitcoin from being hacked. Government will be in control of bitcoins like they control fiat currency and so there will be strict monitoring to check any virtual invaders in the system. Nevertheless, the blockchain is there to add more protection and multiple layers to the secret keys.