Bitcoin is like life for Altcoin, if Ethereum is in position 1 then the ETH market capitalization must be far greater than Bitcoin, that means the price of Bitcoin has to go down to hundreds of dollars, if the price of Bitcoin falls then eth cannot survive, as usual, the price will only go down following the price of Bitcoin.
it is an easy math, since the inflation for BTC is now low (below 2% yearly) and ETH is also low, but above this limit, it relative between number of BTC and ETH in circulation will not change significantly in next two three years, and it is needed for ETH to be more than 1/6 of BTC price, for ETH to overtake number 1 spot, i cannot see that this year, or next year, but it could happen in this decade if both project continue with same development speed
at the beginning 1 BTC was 2000 ETH, today 1 BTC equals more less 50 ETH, and was around 10 ETH at one moment, on large scale this could be seen as dip after first wave, and second wave could bring ETH marketcap above BTC marketcap if development of ETH2.0 goes well, but one has to do their own research before investment