I second this, not just on behalf of myself or DeathofCaine; but on behalf of all once and future Cardhuntareins!
What about weekly events for special cards. These mini adventures get you a card that can only be found in that event. It's a great draw in some other games. Keeps you coming back to get the unique cards.
How about the possibility of community dev of modules? Have a contest and let the community judge as well.