In the very long run, Bitcoin will die as you can't really apply it. Even with coming Lightning and smart contracts, it cannot compete with others. Bitcoin is only for speculation and I agree that it might see another pump this year, but only due to speculation reasons, not because it's a good project.
In terms of market cap ETH will overcome Bitcoin, probably by the end of 2018
ETH is a good altcoin but it will never be able to beat bitcoin.
The only reason for bitcoin's success is 'first come, first serve'. Look at the bitcoin dominance:
https://coinmarketcap.com/charts/#dominance-percentage
It's decreasing for a long time, it just peaked end of 2017, because of a huge number of forks where investors hoped to get 'free money'.
Bitcoin dominance will get below 10% in 2019, that's for sure. In a few years bitcoin won't be in the Top 10 market cap coins anymore.
Give me at least 1 argument where btc is better than another coin. You won't find one.
But as I said, in short term profits are still possible. We might see rates of 30,000$ this year. But this will be due to an increase of overall market cap, while dominance will keep decreasing