I think this expansion is going to have some kind of neutral class cards, like maybe they can used by multiple classes. They changed ethereal peddler's wording and said it was to make it work better with future cards.
So, for example, a spell/minion that can be used by Rogue, mage and warrior, and it's 'class' is 'steamweedle cartel' or something like that. The info so far has been about a unbreakable vault, and a barkeep talking about crime/gang stuff. Sounds like they are sort of tapping into the goblins vs gnomes flavor again, but this time more about heists and mafia style stuff. Maybe there is two factions, and their cards can be used by certain classes each.
It would make balancing easier, in a way. While some cards are better or worse with different classes, it would still even the playing field a bit if multiple classes had access to the same cards. Imagine if firelands portal had been mage/priest/warlock when it comes to arena balancing, or spirit claws was shaman/rogue/mage/druid for constructed. We'd have more archetypes showing up at the very least.