As I understand it, classes will not disappear, the job system is meant to be an addition to the armoury system that allows a player to assume a more defined role in a party. I only have one question in regards to this however, if I am tossing the occasional cure to the tank as an archer while on a dungeon run, and playing the hybrid DD/backup healer effectively and skillfully, why then would I want to be a job where the only thing I can do is heal and nothing else? As Renshi said, it may be better to wait and see how SE implements the system before we pick it apart, though I am hoping they considered the question I just posed.