There's an old saying that goes: "Misery loves company". This phrase will be very true with Don't Starve's multiplayer expansion called Don't Starve Together.

JoeW from Klei Entertainment had this to say about the expansion in Klei's forums:

Don’t Starve Together is a multiplayer expansion for Don’t Starve allowing friends or complete strangers to survive together, in either public or private games. As far as we know, it will have most of (if not all) the normal features in Don’t Starve, balanced for multiplayer, and potentially even add new features.

Right now the goal is to have a minimum of four players on screen simultaneously. This expansion will be released on Steam first just like the original game and the Reign of Giants DLC. No word on whether the expansion coming to the PlayStation 4 version.

This will be free to all of those who have already purchased Don't Starve. After the alpha phase of the expansion the price of the original game will go up to $19.99.

This expansion will be tweaked somewhat for the purposes of balancing but it won't affect the single player portion of the game. The single player will remain intact in its original form.

As of now there is no solid release date beyond "late this summer." Klei plans to have an early alpha for the expansion before it goes to Steam Early Access beta in the same way they did with Don’t Starve and the Reign of Giants expansion.