The character of Doctor Alexandria Hypatia is an on-the-nose reference to Hypatia of Alexandria, an historical figurehead of the scientific schools of Philosophy and Astronomy.
Most of the original characters don't return in this game, but a handful are mentioned. Overseer Martin, Lord Pendleton, Lydia and Wallace go out through story related means. Samuel the Boatman, and Callista have mentions of what happened to them, and nothing yet on Pierro.
The third time in the Dishonored franchise where the Main Protagonist (Emily and now for the first time, Corvo) is given a voice. The first and second being Daud in Knife of Dunwall and Brigmore Witches.
Rosario Dawson and Vincent D'onofrio previous costarred in Daredevil (2015-) as Claire Temple and Wilson Fisk/The Kingpin respectively
The first major patch - New Game Plus - was added on December 19th for all platforms. PC users got 7 day early beta access.