Obviously , it's nearly impossible for Bitcoin to realize permant and global circulation due to its high price and scarcity, which renders it harder to take the place of fiat but it sounds that ETH is likely to be an anchor and a tool for daily use alike, surpassing BTC is feasible.
They say, if a country is at war or in upheaval, buying Bitcoin is not wise for its high volatility and USD is a better choice.
First we need some update about Ethereum is not a cryptocurrency it's simply open source blockchain with smart contract, so it's not possible for this to replace on other hand bitcoin is decentralized which is never been loved by any government because they never allow us freedom they want to check us through our paper currency movement.
We should also think that we would having some disadvantage for using digital currency may take some fees and its price is fluctuation is also the biggest issue because many things need some quick action from us but with this we cannot do this all very quickly.