If we base it from prices I would say bitcoin will still be the most expensive coin more expensive than ETH, but in terms of performance and growth I think ETH will rule that line. It might growth to a few thousand $ increase in value however it will not defeat the current price of a BTC maybe not this year but I see a lot of potential of ETH to replace BTC in the coming years. Due to increasing transaction fees of BTC people will soon think of other cryptocurrency and that could be ETH. So if you are still starting out i would really advise to start with ETH rather than BTC if you want to earn large profits.
In general, I share your opinion about ethereum. I think in 2018 it will be more successful than bitcoin. But while it's too early to forget bitcoin, the lightning network will soon start working and it can change a lot.
I think you are wrong. However the development of ETH, ETH will not be able to defeat BTC. Why?
Because BTC is the main pair and BTC Pair is always more than ETH Pair. That is why the ETH cannot defeat the value of BTC capitalization.