I would imagine that chapter 5 is only in the early planning stages right now, but here's an idea for it. For it's 8 classes, how about remove the traditional core classes as starting character options and let the new classes from chapters 2-4 be the classes you can create at start. With the other two classes, Anet can use those to make sure the starting selection is more or less balanced for the campaign.
I'm not saying remove support for those classes completely as new armors, weapons, and skills would be apprecitated, but instead set it in a place where the normal core classes wouldn't be trained there for whatever reason.
