If the bitcoin is gone then that is the chance for an altcoin to take their place which will be the top cryptocurrency around the world but that is if the people.will let the altcoin a chance because it was always the bitcoins after all and no altcoins have the chance to proven themselves because of the bitcoins but if they gone maybe the altcoins will be down too or there will be one altcoin that will step up with all of them all and then be the top and trusted again.