"Midnight Sun," the book written from Edward's point of view, started as a writing exercise by Stephenie Meyer. Somehow copies of the first written chapters were leaked on the internet, upsetting Meyer. It is a project that she plans to complete in the next few years, although a specific date for publication is not yet set. As of August 28, 2008, Meyer posted a blog on her site regarding the leak of "Midnight Sun" on the internet, her thoughts on what happened, and her intentions for finishing and publishing the book. She remarks in an earlier post on her site that she just "can't wait out the years it will take to reach publication" so she posted the intro for people to read, then later she posted the draft that was leaked on the internet, so people wouldn't have to search for the illegal copy. Her most recent post announces that "Midnight Sun" is "on hold indefinitely," however there is speculation that she is working on it and will still publish the book.
You can read about it here: http://stepheniemeyer.com/midnightsun.html
I do not think Midnight SUn will ever be released because it was leaked online and this caused a lot of people to read it. Meyer's thought that since it was already released online she might not even continue to make it and she was very angry that it was leaked, who wouldn't be mad.
Sadly it is never going to make a way to our shelves unless Meyer is overseen with a huge inspiration to start writing it again which I doubt. Meyer has repeatedly stated her disgust in the way the book leaked and how it angers her to the point where her inspiration evaporated and she want to reverse the ending of the story in favor of the bad guys. Let's hope that we're hit with a surprise haha.