I think it is depend the reason why bitcoin die. If bitcoin die because of losing trust of people, ETH or altcoin will replace bitcoin because ETH is the second most valuable behind bitcoin. Moreover, if all cryptocurrency are banned or no body use them, both bitcoin and altcoin will be dissapear. However, i don't think this case will happen, bitcoin and cryptocurrency are doing well in the market and contribute important part of the economy, just banks and government afraid of bitcoin while everybody get interested in bitcoin and want to invest in it.