We have the first of many Diablo 4 development blogs.
In the post, Blizzard confirmed that PC players will be able to rebind left-click, giving them the ability to have separate buttons for movement and attack. This is something earlier Diablo games didn't offer, but it's becoming a feature demanded by high-level players nowadays.
Players will be able to re-assign all skills to the different slots, and even bind specific buttons to each slot away from the traditional 1-0 layout.
Blizzard also revealed that it's currently working on implementing controller support for the PC version, another requested feature. This, however, won't result in two different UIs, as seen in Diablo 3. Blizzard is instead focusing on a single UI that works well with both mice and controllers by changing how it flows using the different input methods.
Supporting controllers from the get-go also introduced a different challenge. Blizzard explains that the action bar, the area that shows your health pool and skills etc., worked better for TV play when it sits on the left side. Keyboard and mouse players, however, usually set much closer to the screen, which is where the traditional bottom-middle style works best.
Blizzard's solution was to offer PC players - since the platform can support both input methods - both options and they can choose what works best.
Elsewhere in the post, Blizzard explained its approach to the inventory screen, and the design of item portraits this time around. There's also more about what the studio calls a "monster family" enemy design philosophy.
Diablo 4 is in development for PC, PS4 and Xbox One.