As is tradition with every Dishonored game, the first safe code is 451.
Michael Madsen is the fourth person to reprise a character role in the Dishonored 2 arc. In order of appearance: Erin Cottrell (Delilah), April Stewart (Jessamine/The Heart) and Roger Jackson (Sokolov) were the only ones to return in the main game.
The first Story DLC to be developed as a seperate game.
At this time, it is not described as to how past actions of the previous games impact this one.