Supplements would be cool, like small chunks of cards like Netrunner does. Packs of 60 cards that are like $15. IMO, unless it's Magic, Pokemon, or Yu-gi-oh, there isn't really a huge base for most card games. I see Fantasy Flight ones around, but that's because they are located in the city where I live so there is a base for that due to geography.
And I always step back and try to imagine a company with a game this complex that consists of 3 people, plus they are also publishing other games. I don't know about you, but it takes me a long time just to build a book, never mind trying to create new designs while promoting the old ones.
Wait, genius thought, we totally need to make a Mage Wars cartoon (Netflix would totally buy it), create a catchy J-Pop theme song, and come up with some cute mascot that can only say it's own name. Once we get that going, the game will explode!