Last Sunday on the BAFTAs Kristen Stewart confirmed that BD is going to be filmed, but is not known yet whethe rit's going to be one movies or two.
Making BD a solid, satisfying PG-13 movie requires lots of brains and creativity. SM's desire to make the moive into PG-13 doesn't always suit to her book. There are parts of it, like the delivery or imprinting, that are getting into R-Rated fields. On the other hand, the whole plot is dependent on a sex scene between Edward and Bella in Isle Esme and not showing this in downright silly and disappointing for me and many of the fans.
As swedishskinjer pointed out, Titanic is an example of making a sex scene into PG-13 (though it served its role in the movie, the palmprint always makes me giggle but anyway). Someone with a good perspective could make it work for BD too, perhaps. On the other hand, Remember Me includes three sex scenes as I've read from people who went to the screenings and, still, it's a PG-13 movie. I think we could see better after watching this movie how it could be made.
The delivery "gorish" scene I think is one of the most difficult in this movie. The part is essential, because it shows that Bella's transformation is essential and also leads us to imprinting, shows Edward's commitment to both his wife and child and is generally significant and "hype" part of the book that cannot be left out or change dramatically, since it's the part here we get from the first part of the plot to the second.
I just think that this movie needs a very capable director, considering MR is writing the script (fire her!). Which do you think could be capable of doing this?