Klei Entertainment revealed that Don't Starve's new expansion will be coming to Early Access on December 1, following in the footsteps of the original game and the Reign of Giants expansion.
Shipwrecked is a full expansion, and it requires the original game, but it can work with, or without, Reign of Giants.
The version that will be available in Early Access will be fully playable, though unfinished. Klei promises regular updates with new content and fixes to problems they encounter during the process.
Don't Starve: Shipwrecked is only confirmed for PC and Mac, although Klei admits they "would love" to launch the expansion in other platforms.