We are stuck with this card system as is until the next expansion, that is for sure. They may however, make some adjustments to Divination and possibly the cards too, but they will only be made to the current card effects and not changed back to how they were. I also imagine AST will get some healing potency buffs by 5.1 as well.

As for if the old system will ever return? I highly doubt it, but I've been wrong plenty of times. I really don't want to get into how OP I felt AST was last expansion, so I will just say that I don't see it's previous iteration making a return for the simple matter that it has been scrapped, and things tend to stay that way once they are.