So in Daggerfall I know you could join the dark brotherhood (no idea if you could in arena or not), then in morrowind they decided to make you fight the dark brotherhood in the tribunal expac, and then in oblivion you could once again join the dark brotherhood. It seems that the dark brotherhood has always had a presence in TES games in one way or another, and just wondering what your predictions are for skyrim.
Well the dark brotherhood are Tamriel wide. You could join them in Daggerfall and Oblivion but not Morrowind because they had the Morag Tong. They didn't make an appearance in Arena. From what we have seen, the Dark Brothehood will be in Skyrim as a joinable faction.