Bitcoin is not just a replacement for cash but it is also a great revolution in the economy transfer system as it will change the thinking of people who use it about paying and earning money. Bitcoin payment methods can be more fast and convenient and also secure than a cash payment mods as it is a digital currency it has many plus points over the real cash which we use.
I will be difficult to change whole system and only use digital currency it is mostly impossible i think but bitcoin can be used as an alternative to this some times
I agree that bitcoin can be a great alternative to cash, but as it is now (the technology) it has no chance to substitute cash. It is simply too slow, too expensive and you cannot pay small amounts without getting killed by fee.
Imagine I take the kids for an ice and soda one hot summer day at the beach. Not only can I not buy just 4 ice and soda, without fee at least doubling the amount, I need to buy 50 to make it worthwhile, I also have to wait for some miner to mine a block in order for the shop to confirm my payment – and that only if I really kicked the fee up, or else I might wait 2-5-20-100 blocks.
You need instant transaction / confirmation, zero or close to zero fee and physical light mass / volume. Such alternative already existed to physical cash, its called credit card or Mobil pay.