Well everyone is always looking for greener pastures lol. Most people in crypto wanna get rich quick, Peercoin has been around for a long time and no one is getting rich from it. Since it is unlikely that the price will suddenly spike and take everyone to the moon, people simply gradually move to newer coins that can keep their dreams alive 
If so then bitcoin is probably going to die because people will move to a newer coins? Hmm.. I think bitcoin is already established enough to survive. Also preecoin wasn't recognizable and still isn't, where bitcoin is already knocking on doors of many virtual services, and is being recognized by people that usually don't give a crap about cryptocurrency