I just want to reply even though this is an old post. Based on your expectation, ethereium could surpass bitcoin by summer 2018. Well, the first quarter of the year is almost over and the eth price is still way more behind of bitcoin. It is actually more than a hundred percent lagging for the bitcoin price and I assume that even the end of the year, eth price can't step even half of the price of bitcoin. Nevertheless, it is still a good sign that eth price is continually increasing as the time goes by.
We should not compare these two in terms of price only. As an investor, you should make the judgement based on the returns you are getting on different investment options. Bitcoin prices are already quite high (about $10000) at the time of writing this post. Even with most optimistic estimate, it will be about $30000 by the end of 2018. Now suppose, you invest in $100 worth bitcoins, you will get $300 at the end of the year. If you invest $100 in Ethereum at current price level, you will at least make $500. Similarly, you can get even better returns with other less priced coins.