Telltale made their official annoucement on Twitter today:
As a fan of Telltale's recent style of games, and a huge fan of the Song of Ice & Fire book series, I am really excited to see how this will develop. Will they be tempted to add combat to their formula, or will they focus more on the intrigue and politics? I'm personally hoping for the latter.
The only downside, at least for someone like me who is ambivalent about the HBO show, is that they seem to be working with HBO directly on this, so it will most likely be based on the TV show. (As if the title itself wasn't already an indication.)