In 50 years, the machine will be able to outperform the bottom 50% of the human population in any conceivable endeavor or task behind a keyboard/monitor. So CAPTCHAS will eventually be useless.

So it's an intelligence race. The more intelligent system (a computer, human, or hybrid) will be able to deceive the lesser intelligent system (computer, human or hybrid).

So the problem changes from: "Is the entity I am dealing with a computer or a human" to: "Does the entity I am dealing with have intentions to gain an unfair advantage over this transaction."

Humans have a part of our brain where we look for how others might be taking advantage of us, the algorithms and data structures there are remarkable. Computers will need to acquire those abilities if they are to manage the exchange of money, goods and services.