As of now, there is no altcoin that can replace bitcoin. It had been the most successful crypto, people see bitcoin as the main cryptocurrency. It is too far from reality for ethereum to replace bitcoin at the current state since bitcoin dominates the market.
There is no way Ethereum can replace bitcoin even in any state because you cannot compare the two, Ethereum is premined shit which cannot be viewed as a currency and that is the prime difference and there is no crypto in the market that have the technical capability to override what bitcoin is capable of but may be in the future we might see some coin development which could accommodate more users.