That is a question that only Stephenie Meyer has the definitive answer to.
I do hope she does publish it one day.I did get to read some of Midnight Sun years ago(up to ch.12) on her website,but someone (NOT Stephenie) leaked it online and she pulled it from the website.
She was going to release Midnight Sun on the 10th anniversary of Twilight back in 2015,but EL James (author of Fifty Shades of Grey) was releasing a book in Christian Grey's POV,and Stephenie decided to release a special anniversary book marking the 10th anniversary of Twilight,Life and Death(with a gender switch)
She could hopefully change her mind down the road and publish Midnight Sun.I for one would love to read Midnight Sun in its entirity.
