They have gone for a sort of a cross between 2nd and 3rd Edition, in 2nd Ed you had 4 Groupings (classes within each group):
-Priest: Cleric, Druid, Specialist.
-Rogue: Bard, Thief, Ninja (added later).
-Warrior: Fighter, Paladin, Ranger, Barbarian (added later).
-Wizard: Mage, Specialist.
Now we have 10 groupings (classes), classes (subclasses) within each group.
I believe they mentioned settings containing subclasses, so a Dark Sun book might have new subclasses for each class, same with Ravenloft (Rogue: gypsy, etc), etc.