Rather small card pool of 120 cards is currently available on the beta server. One had thought this may possibly be the first core set; however, it turns out that this is not the case.
The original discussion started out by a forum post requesting changing some cards balance due to their identical stats other than the difference in faction. Following is a reply from Lightmare employee.
The second set is intended to have another 120 cards, I urge you to accept that the game is meant to be balanced and more playable on a larger scale with ALL of the cards in the game. Again, I understand the frustration this will cause but there is NOTHING we can do about balancing the game around every single aspect without adding more cards, which is our short-term intention now that we’re about to launch trading and the GUI.
So yes. here is confirmation that there will be at least 120 more cards coming before the official launch of the game. This is a way more than simply predicted additional cards to make up the lacking cards in Zombie faction.