I predict Ethereum will someday overtake Bitcoin. Realistically, it is just a lot better of a cryptocurrency all around.
ETH is something that has been serving as the alternative for the bitcoin. Ethereum slowly gaining more power and the same won't replace the bitcoin growth. Ethereum has been gaining more potential as more and more ico tokens were getting developed on the same Eth platform.
Maybe because nowadays there are many cryptocurrency came out when bitcoin become popular, but i know bitcoin will remain while other just pass away. And since bitcoin have many users perhaps it will become number one in all cryptocurrency for long time.