Given that Summit is determined to maintain a PG-13 rating for Breaking Dawn, despite its more mature content, the MPAA Rating Board will have a big say in whether Breaking Dawn is a compelling film release, or a cheesy wait-for-DVD whitewash. From the Board's website:
"More than brief nudity will require at least a PG-13 rating, but such nudity in a PG-13 rated motion picture generally will not be sexually oriented. There may be depictions of violence in a PG-13 movie, but generally not both realistic and extreme or persistent violence...Movie ratings are determined by a full-time Board of eight to 13 parents. Raters have no prior film industry affiliation...The Rating Board is led by senior raters who administer the process, whose identities are made public in order to increase transparency in the system and to enable them to communicate directly with filmmakers and the movie-going public...Recognizing that many filmmakers strive to make films of a certain rating, senior raters routinely make themselves available for script consultations and calls from the set, to answer questions about rating guidelines as filmmakers bring their creative visions to life."
As such, it may be that the only way a PG-13 Breaking Dawn can avoid a cheesy fate is for Stephenie Meyer -- as a churchgoing parent herself -- to lobby the Board directly. And I'm sure it wouldn't hurt if Twilight fans lobbied members of the Board behind the scenes.