Ethereum or Litecoin would probably take the place of bitcoin. If bitcoin were to die tomorrow, it would probably drag down the altcoins with it as well, but if you give altcoins some time until they can establish themselves, they wouldn't be harmed in my opinion. An altcoin may eventually take the place of btc as the best crypto as well, especially considering the scalability issues that btc might face in the near future.
Yep. Crypto is not all about Bitcoin really but we do know that Bitcoin played a huge role in shaping the cryptoworld. If people lose interest in Bitcoin then for sure there is a better coins who rose which will take its place either a new one or an existing one.
Ethereum is the 2nd biggest market next to Bitcoin so it is not a surprise if it will take Bitcoin's spot if the network can't scale and losses its demand.