For the new movie, I must admit that I feel the actress cast to play Umbridge is far too attractive compared to how the character is described in the book. I've always liked Helena Bonham Carter and she should make a great Bellatrix Lestrange.
I did go check out the post by the guy who claimed to hack into the publisher's computer. It is not very detailed, and would explain what 'major character' is going to die, as J.K. Rowling stated. Believable? I'm not sure--I'll just have to wait and find out.