Right before Dragonborn's release on Xbox 360, an alleged beta tester leaked details on Skyrim's latest DLC. It should be noted that the beta tester's status is unconfirmed and all of the following is rumor until proven otherwise.
According to the leaked info, Dragonborn doesn't require the completion of the main quest, but different dialogue options will be available if the main quest is completed. The DLC starts off with Cultists of Miraak attacking the player on their search for the false dragonborn. Looting their corpses will reveal information about where the cultists come from. A boat can then be taken from Windhelm to Solstheim, the setting of the DLC.
Solstheim has a discrete map and is approximately the size of the Reach near Markarth.
New factions include a werewolf pack located at Frostmoon Crag and the Morag Tong, the Morrowind assassin's guild. Unfortunately, the player cannot join the Morag Tong and the only level of interactivity available is to fight them.
New enemies, locations, armor, weapons, spells, and shouts will also be available.
Considering that Dragonborn is hitting the 360 tomorrow (priced at $20), we'll be able to see the validity of the details that the beta tester leaked.
PC and PS3 players will have to wait until early 2013 to play Dragonborn. This is especially happy news for PS3 players, who have thus so far been spurned in getting Skyrim DLC due to technical issues.