Bethesda and Arkane have announced that the next update will come next week, and that it'll include the anticipated custom difficulty and mission select/restart.
Custom difficulty will let us adjust more than 20 different aspects to suit our needs and wants. Some of the examples includes how effective sleep darts are, how many enemies that are likely to attack at once, and how fast we get spotted. If that doesn't sound challenging enough we're also getting something called Iron Mode. This will activate permadeath and won't let us save or load manually.
Then there's mission select/restart. It's just as it sounds. We'll be able to replay any mission we unlock after the update is installed. Though it's worth noting that these selectable missions will retain the status of our playthrough at the start of the respective missions.
These are just the most noteworthy inclusions, and we're told that it'll include even more fan requested changes and fixes when the beta version launches on PC January 18 and in full on all platforms January 23.