As most of my shopping and bills is all paid electronically, I generally don't carry cash on me because I just don't need it. Another reason for not carrying cash is that I'm a recovering addicted gambler. At one time in my life it was a real problem and a part of my strategy is not to carry much cash on me because it's too easy to lose it gambling in the chance that I might win the jackpot. False dreams and it was a hard lesson but I don't go in that direction any longer. I think that the need for cash is much less these days but I don't think it will disappear.

our world is going to end soon because of money and overpopulation

Perhaps, but not in my lifetime.

Short answer, no.

Money is just anything used as exchange for services or goods that is universally acceptable because it is extremely useful or was useful at the time. It was salt at one time, which protects food from spoiling, food itself,(because what’s more useful than food) like grain, that didn’t spoil quickly, - Eventually it was turned into metal coins or gold, which really has no use besides it’s conductivity and aesthetically pleasing appearance. It was debatably a thing to use because it was based on a somewhat finite supply and had real value based on that supply and wasn’t based on faith. - I’m no expert on currency or monetary systems, but this is how I understand it.

If the human race ever reverts back to being hunters and gatherers

Money is a tool of exchange for goods and services. I certainly hope that some form of money continues to exist, because I have need for goods and services.

No, the world revolves around currency.

No. Certainly not ! But it may one day exist under a paradigm of absolute, democratic, public ownership and control, wherein there are no private banksters owning it, or leasing it and making commissions off the lending of it to borrowers.

Where there is trade, currency will follow.

Star Trek: Trade and gold pressed latinum.

Sure there will be a time when money does not exist, but humankind will also be extinct.

No - money is just the easiest format of exchange for goods and services. Now we see how even computer code can be a form of money, so it will always be around maybe just in different formats.

I think we're getting there now.
I don't know if cash will ever disappear completely, but most of our transactions will be electronic if they aren't already.

Gene Roddenberry was definitely a socialist.

No, I don't think we'll ever move away from some form of currency. We're likely to continue to move away from paper currency as technology advances, but most likely all transactions will be done over the information super highway by then.

Should there be some kind of apocalypse where all technology is destroyed, there by sending us back to the middle ages, we'll simply go back to the barter system.

There will always be some form of exchange currency-- something they attach value to, to be used in exchange of goods and services.