Queen of Thorns - no, they haven't said she won't be in it, but just with the meddling that the Tyrell Bobsey twins (Margeary and Loras) are up to with Renly, I get the sense that introducing Olenna seems redundent. From the books, I always got the sense that she was running just about everything in House Tyrell on the subtle side, what with Lord Tyrell being a bit of a boar. Perhaps they'll bring it forth that she was mentoring Margaery, but I always got the sense that the girl was left in the dark on a lot of things, due to youth and due to her percarious position of being the one to be wedded off. Can't have her betray the family.

In this vien, I don't mind seeing Ann Boelyn play Margaery... but I had her younger and fairer. Seems an odd choice, again, makes me think that they just won't bother with the meddling old lady.

I hope I'm wrong, but just looking at it from a TV maker's perspective - you don't bring in redundency and by book four there are so many characters... you just can't have them all.