Ugh, I would rather Sophia didn't play the part, because I assure you, she would never be taken seriously in her career ever again. I just know that the movie will be horrible. And I doubt Robert will star in it, considering the book is based on a Twilight fanfiction, and he hated Twilight. Let alone that he would never be taken seriously ever again for starring in an adaption of that horrid book.
So, every actor/actress who values his/her career won't be a part of that franchise.