There isn't much we don't know about them now. With House of Wolves we learned a vast amount of info about them. We know that Kell of Kells is their highest honor and ranking, and he even integrated vex tech into himself, so he was even above the traditional rank of Kell of Kells. So they're not really much to challenge us anymore. Also, with Verriks on our side, there's a good chance he'll unite the houses, become new Kell of Kells, and being the fallen over to our side.