I really think ETH is going to take the number one spot, ETH is slowly growing, it's just a matter of time. Bitcoin is way older than ETH, Only if ETH was older than BTC, we would have been saying a different story now
But i do not think so. because etherium is still too much fare away from bitcoin, bitcoin is still becoming more stronger, the popularity of bitcoin is still increasing, because moe and more people are entering in the world of bitcon which is making bitcoin more stronter.