Well I haven't read the books but since Cersei is townie, is it possible that Tyrion and Varys might be the scum along with Dabaerys and the second faction might be White Walkers?
Highly unlikely. I'm pretty sure this book focuses more on the things going on in the Southern territories. Like I mentioned earlier, it focuses more on the Lannister's and the events occurring in King's Landing as well as the events in the Iron Islands and Dorne. We probably won't see any reference to White Walkers at all in this game and maybe not even Daenerys either.
Yeah Tyrion and Dany were completely absent from that book. It was almost entirely focused on Southern territories of Westeros.