But that doesn't necessarily mean that cash will go away, I think people are attached to cash a lot and it's a different feeling when you have cash.
In my opinion, your opinion is true. Why ? Indeed, cryptocurrency is now much interested, some people consider cryptocurrency as a valuable asset to them. but cryptocurrency has one weakness that is not the official currency. cryptocurrency is just a virtual currency in the digital world. so this is where another function of cash is to be a medium of exchange for cryptocurrency, so the selling value of cryptocurrency can be used for in the real world.
Always remember, if people get more interested in learning BTC and crypto, always remember that there would still be people that will state negative thoughts and false news about BTC, and in that way it can either be a downfall since people will spread false negative news and at the same time it won't be healthy for BTC and crypto once people sees the wrong idea, though I understand how helpful BTC and the whole crypto can be in the economy of our own countries.