After watching season two, i am thinking there could (should?) be expansions to this game. Definitely nothing like the lcg, but extra house packs would be plausible for sure. Initially i'd have thought of an expansion per season, but i'm thinking that they'll have to wait for more characters to be introduced.
House Baratheon seems like an obvious option, with Stannis, Renly, Melisandre, Ser Davos (an sons), Saladhor San (sp), etc. It's pretty complete just like Lannisters and Starks.
House Greyjoy and Targaryen are both starting to make sense too with much more coming in season three, leaving House Tyrell and Martell for last.