Agreed that the entire market is not only bitcoin. However, most altcoins exchange to bitcoin, because bitcoin has a higher value. Thus, when prices of bitcoin fall, they other altcoins as well will. However, you are correct in the sense that ETH has a strong claim to keep the crypto world going if bitcoin dies. ETH is becoming much popular especially for the use of ICO payments. If ETH can continue to have a "everyday valuable use/need" it will survive. As for the prices of ETH I can't speculate on that now. But it looks like its still really tied to the behavior of bitcoin very much.