Etherium is a better coin since it also has the smart contract feature. There is nothing that you can do with bitcoin but you cant with etherium. So why not all people sell their bitcoin and buy etherium.
If everyone will going to sell their bitcoin it will result to slight value decrease of bitcoin because the selling demand will going high opposite reaction to ethereum because it will going to increase the value because of buying demand is going to be high. Maybe you are now investing in Ethereum that's why you want everyone to sell bitcoin and buy ethereum. Why don't you divide your capital for both because this top two coins is promising then you will earn from both too.