it will come out eventually but not for a very long time she had to put finishing it on hold because it got leaked on the internet wewe can read the first 12 chapters at this website stephanie meyer also explained about midnight sun here at link
according to the stephanie meyer website she ilitumwa that after the first part of breaking dawn comes out and things start to calm down a bit she will finish midnight sun and mayb later one she will make zaidi vitabu for the series but all of this wont happen until the first part of breaking danw comes out in theaters hope this helps :)