Cash can't be replaced soon. We've been using it for centuries it's going to stay with us. Rural communities suffer because govt's put city ppl in the middle of their plans. In some rural communities ppl don't have smart phones so they'll use cash or sms to pay for goods & services.
That does not mean cash will disappear anytime soon because it is still quite needed and not only in rural areas because in urban areas itself there is still quite a need for transactions using fiat currency in everyday life. Except if we are talking about developed countries because access to payments is utilized in much easier things and the use of transactions is starting to be developed using other than cash.
In the near future cash is still quite needed and I do not see any urgent need to not use it even though currently some people prefer to make payments using credit cards or other products that have similarities and cash still has a place as a process of paying for goods and services.
Cash won't e gone forever, but which cash do you hold? That matters the most. Like during a war, is holding the cash of the war thorn country makes sense? Or is it smarter to hold cash from a fiat that stays strong? And which one will make any sense? Bitcoin makes sense because of this, because if you are holding bitcoin instead of cash, then wherever you go, then you can cash it out and make money from it and the value will not drop as much.
It is more volatile than a currency, but that doesn't mean it always goes down, sometimes that means it will go up. You can look at current bitcoin and say it went from 100k+ and into 90k, which is a drop, or you can look at it and see 20k became 90k and see how much it went up.