Dishonored 2 only just hit stores on November 11 for Xbox One and PC, but Bethesda has already detailed a bit of new free content coming in an update. Specifically, a free update to be released some time in December will add a New Game Plus mode, along with custom difficulty settings.
If you're unfamiliar with New Game Plus, it's a mode that's typically unlocked in some games after a player finishes the game at least once. Depending on a game's particular implementation, you're sometimes allowed to keep items and experience from your first playthrough while you start a new game. The game may also be more challenging or offer features not available in the first playthrough.
Bethesda didn't provide any exact details on New Game Plus or the custom difficulties, but we should expect to hear more ahead of the patch's launch. In any case, you can expect some added difficulty modes to hit Dishonored 2 next month — maybe in time for your second or third playthrough.