ETH has a long way to go to pass the price of BTC. I think even in 2019, BTC will take the lead. May be forever? Who know. Let's see
People always compare eth to bitcoin although price are volatile investors still use bitcoin. Exactly it takes time to surpass bitcoin. So I think eth cannot pass btc because users are into btc who believes the future.
It's not possible if ethereum will always pegged to the bitcoin. When bitcoin goes down and it follows and otherwise ethereum will always stay below the bitcoin. If that can become independent and it gives a lot of chance to the ethereum to surpass the bitcoin but it'll take a very long time.