There may be a limit of classes... but they are promising very distinct storylines. The replayability may be in the story if what they promise is delivered

True there may be limited playability in class aspects... but truth be told, how much difference is it to playing a lock, then a mage, then a shadow priest, then a balance druid.... they all casters.

Even with the standard MMO you have 4 main archetypes anyway... tank, healer, melee, range. No more, no less, just variety. (lesser archetypes/varieties are pet controllers, crowd controllers)

Just depends on how much of the design will be compromised to push the games rollout and balance imo.