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.
Bitcoin may not be the number one sponsor for a long time because there is nothing that can always be number one, but it will take at least several decades to replace Bitcoin. Therefore, to enjoy investment and play between bitcoin and currency, you will never know what will happen tomorrow.