I think it will simply become impossible to keep digital payment systems secure. The whole online economy will collapse. Amazon will become worthless. People will actually have to go out to local stores to buy everything. People will have to go to their local bank or currency exchange to cash their paychecks. The credit card system will fail completely too, while payday loans will take their place. The stock market will have to go back to traders yelling their trades to each other at exchanges. The old ways will become new.
There is always an arms race between offense and defense. The defensive side has to succeed every time. The offensive side only has to succeed often enough to shake the public’s faith in the system.
People already successfully hack financial institutions, it’s unavoidable, but it’s not going to change the world in the way you suggest