ETH will likely stay behind BTC for a couple of years and eventually overtake bitcoin. Ethereum offers several opportunities for businesses to take advantage of while bitcoin will be the currency of the elite.
It is never ever going take throne from bitcoin because it does not have that capacity. Bitcoin is the one which is leading the market for years rather since the creation of virtual currencies. Ethereum leading the altcoins clan is digestible but overpowering bitcoin is mere daydreaming, nothing else. We all should keep in mind that bitcoin is enjoying legalization as well which is not given to most of the altcoins.