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.
Both really. I don’t think it’s too far of a logical jump to think that an AI programmed to maximize profits would decide theft is the easiest method.
Edit: the AI wouldn’t have to be sentient, just amoral.
An AI programmed to maximize profits with no restrictions coded to stop illegal activities would still be an example of someone using AI. Regardless, if you believe AI will be powerful enough to shut down financial institutions as an industry, why would you not also believe AI is just as powerful at defending against attacks. At the very least, finding the perpetrator before they get much of a chance to use their stolen money?
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