Maybe someday ETH could overtake BTC thrones but then again the dominance of BTC could always increase so fast.
Bitcoin's price has been increasing recently, but still not enough to cover the cost of mining a single coin. In fact, it has been reported that some miners have been losing money. If Ethereum continues to rise in price, large mining pools will switch back to mining Ether over Bitcoin. BTC prices could stagnate as more miners turn back to ETH. If this occurs, ETH might overtake BTC in market cap and become king. I also thought, maybe it's just a matter of time.
The last time I checked, ethereum was moving to POS, that's prove of stake. This means that miners won't be needed for ethereum but investors who are willing to stake their ethereum a minimum of 32 ethereum. This has been fulfilled in the ethereum 2.0, though it's yet to be completed.