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
Bitcoin is different, it's in a league of its own, it is unlikely that it will fade away in this manner. Everything is relative to BTC, most coins don't have a dollar value per se, they have a BTC value. Cryptocurrency penetration into the real world is being built primarily around BTC. Peercoin was an attempt to bring something new to the table but it failed to hold the attention of people, unless the devs add some cool new features, it will remain a coin for die hard fans and bagholders.