Remedy has officially announced two upcoming paid Alan Wake 2 expansions to be released starting next year.
Any player who purchased the Deluxe Edition of Alan Wake 2 will receive the expansions at no extra cost, though they will also be available separately for anybody who purchased the base version of the game. Remedy outlined the exact nature of the DLC to IGN:
Expansion 1 - Night Springs
"Visions and dreams. Fiction is written and coming true. Fiction collapses and remains just words on a page. These are those stories… in Night Springs. Play as several familiar characters from the world of Alan Wake and experience the unexplainable in multiple self-contained episodes of Night Springs, a fictional tv-show set in the world of Alan Wake."
Expansion 2 - The Lake House
"The Lake House is a mysterious facility situated on the shores of Cauldron Lake set up by an independent government organization to conduct secret research… until something goes wrong. Explore the Lake House and embark on two separate adventures as the realities of Saga Anderson and Alan Wake collide again."
The first DLC expansion is currently scheduled for release in late Spring 2024, although the IGN article notes that Remedy has stated that the release window is subject to change.