Bitcoin certainly is the radical innovator and Ethereum or other Altcoins are more or less incremental innovators. But if you look at Daimler Benz, who radical innovated carriages, others also pushed for innovations. Ford innovated by mass producing its product and lowering its costs (this could be smart contracts like Ethereum or Privacy like Dash, Zcash or Monero), Porsche found a niche for sport cars and so on.
And maybe we could see something similar in crypto as well. Bitcoin will probably stay, but there will be a crypto currency focused on privacy (as it might be outlawed in some or most countries), Ethereum might have found its niche for smart contracts and radically trying to push forward and maybe a more centralized smart contract currency like NEO or Cardano is more suitable for restrictive goverments to adopt like China.
So yes, Bitcoin probably will be king, but there might be space for a couple of other crypto currencies, doing things Bitcoin doesnt want to or cant do.