I will be not surprised if it happens one day, as Ethereum has more functions than BTC. I am sure that still, ETH is undervalued. However, we cannot wait for its great growth very soon. Suppose that everything will begin in 2020, after the launch of Ethereum 2.0 and Bitcoin halving.
Then, we can see ETH offered for at least 800-1000, and it will be not the top trice for this cryptocurrency.
So, if we say that Ethereum has more function than bitcoin, then why is Ethereum still lagging behind? I have used both technology and I have really not found anything that is much more different or more spectacular that Ethereum offers that bitcoin does not. I really dint think there is any point comparing both of them because they can never be compared in any way, bitcoin will always remain the only one coin that has all the functions that is needed to make cryptocurrency be recognized globally.
In future maybe when bitcoin reaches some amount, Ethereum could go to that $4000 because if you really take a look at it, Ethereum has always been growing because of bitcoin bull run, and even the last all time high that Ethereum had was during the bull run of bitcoin.