I thought for sure it would take until the end of 2018 but it looks like this summer ethereum might pass it up. With the turmoil around BTC potential splitting, it might be very soon. IMO this is healthy, we will always value bitcoin for being the one that started it all, but it's time for a more dynamic and adaptable currency to take the lead.
It is true that bitcoin is the number one crypto currency, but only because it is the most popular and most widely used. But it is not the crypto currency with the highest price, which is actually suitable for investing. Since a person would not be encouraged to invest in a crypto currency trading if it has very low or very high prices that would be too cheap or too high for someone to be interested on it.