That's never going to happen, even if ethereum upgrades to ETH 2.0 and introduce the proof of stake ability ethereum will still remain the number 2 on coinmarketcap and in crypto space, the highest this update can do is price surge
I completely agree with you, I think not only ETH, but also other alts will not be able to overtake Bitcoin, not now, nor in the future, Bitcoin will always be number 1 on the market and will always dominate.
ETH is really one of the best coins and has more potential to be on the first place. But it doesn't mean there can be any altcoins, which can overtake BTC. It is just impossible to happen that. But if we are talking about ETH will be able to take 1st place in 2020. In my humble estimation, ETH will be number 1 among other altcoins.