Actually to make it specific, bitcoin can't replaced by cash but to convert it to fiat. Replace is different to convert. As time passes by many establishment accept bitcoin as their mode of payments, well for only those country legalized bitcoin of course. Bitcoin is really demand and popular here in social media that makes everyone amazed on its value and many are getting involved to benefit on it's capability for each and everyone of us here in crypto currency community.

this is only the case because the world still thinks in US dollar, you have to think beyond the US dollar, how will the world evaluate assets then? it will be called the "coins of style"

Unfortunately its an absolutely yes, bitcoin can't replace currency in the due to its pricing is not stable. Unlike native currency it was use every nation and it was accepted nationwide even in ordinary expenses that leads to its stability.

Yes, I really agree with you. Indeed from the beginning the main function of bitcoin is just as a commodity (like gold) and digital assets. There are special terms and conditions for making something into a currency, one of the conditions is a stable value.

Bitcoin cannot become a global currency because each country has its own currency. But the price of Bitcoin is currently unstable, but I think this is only a phase and the future of Bitcoin will be very good.

Bitcoin is certainly not a globally accepted currency and it's not currency at all it's just used as store of value. For bitcoin to replace fiat and become globally accepted currency it would require some drastic changes to be made in bitcoin. If there's something which cost you $1 in fiat currency the same thing would cost you more than $1 because you have to add network fee to $1 so obviously you will choose to pay with dollar instead of bitcoin so it's not just instability in the prices of bitcoin which stops it from becoming a worldwide currency but the other factors like transaction fee etc also is a hurdle in bitcoins becoming worldwide currency

Personally, I think Bitcoin can replace cash, used to buy goods, exchange. For this to happen I think people need to develop more applications that meet the needs of people. If the bitcoin price is stable, we can use them as a deposit in the bank. Buy bitcoin merchandise through bitcoin card issuance.

I disagree. The price of bitcoin would be much more stable if it were adopted as a world reserve currency, held by central banks. The reason why bitcoin has been so volatile is because of growing pains as a relatively new technology.