Impossible to happen. If we talk about die meaning no value, no uses, no existence and no improvement. Meaning if bitcoin everything will wash out because everything that bitcoin started will gonna die. Altcoins can stand alone if there will be leader without bitcoin. On that altcoins can survive because they have the leader. It is hard to say exact things to happen if bitcoin die because very impossible to make it happen. Look even bitcoin goes down it will recover and back again.