Since Alan Wake 2 was released a little over a month ago, Remedy has pushed out some updates, mainly focusing on polishing the game and removing bugs and other technical concerns. But there is also some new content to look forward to in the works.
The game's official X account recently posted "New month, new game... plus?", which should reasonably mean that New Game Plus is coming in December. Previously, it was also confirmed that New Game Plus also comes with Nightmare difficulty and a few other goodies.
An exact date for New Game Plus has not been confirmed yet, but we will most likely find out soon enough.