It's possible but unlikely. If it did happen, I hope it would be something more advanced, since these other cryptocurrencies are basically Bitcoin clones with a few parameters changed. What difference does it make whether you use Bitcoin or Litecoin, other than the possibility that you might win the lottery as an early adopter? (Let's face it, that's the only reason people care about the other cryptocurrencies.) I want something with Zerocoin style anonymity built in from the beginning. The reason I think it's unlikely is the same reason that alternative social networks have a hard time competing against Facebook, and other markets have a hard time competing against Silk Road. The value of some systems is in the network of people that use it. Everyone goes to Facebook because that's where everyone is, so they can create an account and instantly find a large number of their friends. Everyone uses Silk Road because this is where everyone is, and you can find 150 page review threads for any product or vendor. That's by far its biggest asset. If Bitcoin is already widely adopted, there will be a lot of traction against switching to yet another cryptocurrency, even if it is technically superior. Atlantis started with Litecoin and added Bitcoin because it was the number one requested feature. So even though it's easy to support multiple cryptocurrencies, if everyone is using Bitcoin, why bother?