Ethereum kinda replace bitcoin but dont forget monero (XMR) Im trying to mine monero now the price getting rise day by day
Eth cannot replace Bitcoin because they have different purposes!!
When searching for the coin that could explode in 2018 just look at their team of developers and things on their roadmap. Also take into consideration their ability to stick to the roadmap.
I would believe that lisk ,waves , ark , tenx(great team) will make you rich in 2018.. As for Dash I just dont see anything new brought to the world with this.. and because of the masternodes idea, it feels like a ponzi waiting to explode