No details were released — only this presumably non-final cover, given that it lacks the designer credits and other details you might expect to see. For this title and others, FFG gave no release dates, which makes sense given that release dates are often bunkum these days thanks to continued issues with manufacturing and shipping.
Along similar lines, FFG announced Descent: Legends of the Dark – Ghosts of Greyhaven, and this expansion can be incorporated as a side story in the Act I campaign included in Descent: Legends of the Dark, or it can be played as a standalone adventure, although presumably using components from the earlier standalone game. Act II of Descent: Legends of the Dark is in development.