I haven't read any of the past comments.. However I'll post my thoughts:

Yoshida spoke a few words in a past letter on the "Job System" - Not to be confused with the Armory System - and if I'm right, and I don't believe I'm reaching in saying this, then I think the Class name changes are going to be integral in the future shaping of classes.

For example.

Marauder becomes Warrior.

Warrior can progress down several paths as they progress.. Maybe at level 50.. I don't know, but maybe Warrior can then progress INTO Marauder as an advanced class. Gaining access to an exclusive and different skill set that Warrior wouldn't have.