Personally, I will never see this happen. Crypto will exist but fiat will exist as well. They will co-exist because they have different features.
We both need fiat and crypto. In my opinion, we can reap the benefits of both crypto and fiat so why any of the two should disappear?
But as you can see sooner or later the fiat will positively replace by crypto and digital wallet so on and so forth, have you aware of the implant like a usb?, on the person wrist?, which it will be the new paying system though.
And right now there are tons of country that implementing it. On the other hand yes it has a bad effect but nevertheless i think it will serve as a concept of the future.