According to O'Malley, they are using a different ending than what he has intended for the books (which removes the need to have O'Malley do a rush job on Volume Six for the 2010 release of the film), which means that things will turn out significantly different.
Have you read Volume 5, yet? I'm wondering, based on that book's ending and the fact that O'Malley seemed to foreshadow another appearance from Lisa for the finale, whether things will turn out the way we assume they will.