Well if HBO wants it done right, yes. Having said that, throwing hundreds of characters and subplots out there won't be good. I suspect some minor events/characters/subplots will be left out or merged and still have 4-5 more season. Same as the LOTR trilogy.
New cast members for season 3: Word of warning, no real spoilers, but the names of the characters are (of course) revealed.
Diana Rigg. I like it. She was terrific in Mother Courage. Im sure the Queen of thornes will prosper. One of the bigger names they've taken on.
Not the same actor. Yeah, I know I'm over 6 months late to this party. Sorry, I got stuck in traffic.
I'll be honest, I haven't read through all 25 pages, but I will say this, Game of Thrones (S1/S2) is one of the best shows out. No doubt, it's popular, and for good reason. I hear the production costs are astronomical, but who's keeping a budget list (Kidding)...