To answer the original question... you can't destroy the economy, so I'm not worried. You can destroy the financial system, but not the economy. So long as some people want things that other people have, and are willing to pay for them, there will be an economy.
As for people being put out of work by machines.... this is already happening and has been a continual trend. There won't be any one moment when suddenly machines replace everyone, but just the slow gradual automation of various tasks that we have been living with for decades now.
But what if machines can provide enough for everyone? Anything? Need food? Poof, your machine provides
Need alcohol, drugs, love? poof, poof, poof.
You're machine broke? There's a repair machine on its way..
the future is as simple as that. Mayby the economy will still exist, but in the virtual world of the machines. Humans will have gone beyond those earthly concepts and evolved in a more higher species.
Human greed is limitless, human desires are insatiable, but just human envy alone would waste any machine in less than no time.