According to a rumor that started over on the forums at MTG Salvation, the answer is yes. It is being said that in the source code they have found card names previously unknown. Now this is just rumor, but they believe it might just be cards that are waiting to be unlocked. They are leaning towards the idea of DLC, as they have managed to extract card names, details and art from these source codes. If they are correct, these new cards will cover all your basis, a little for each manna, as well as new and old decks. Now we all know that speculation is just that and will not be confirmed until the first DLC pack is released (or close to) and we get to see first hand what is in it.