Aesthetically, I’m not a huge fan of Dark Mode. I think it restricts the colour palette for other elements (such as tab bar tint colour) leading to repetitive apps that have no distinctive personality: everyone trends towards dark backgrounds with blue and orange accents. This is especially true if Dark Mode means a theme that is meant to be easy on the eyes at night, not just an appearance style that is predominantly dark. Windows Phone attempts to combat the boringness of black with rich animation and fancy transitions, to some success. Even then, Microsoft is pivoting away from the darkness with recent software revisions, adding more vibrance and bright elements.
There’s also no getting away from the fact that a lot of apps are comprised mainly of full-colour photography feeds, like Facebook and Instagram. Full-colour images look terrible with dark chrome in scrolling lists; by their nature of being photo-realistic, they can’t match the surrounding UI. Dark Mode is crippling for these uses and it just so happens these uses are very common tasks for phones. What I’m saying is, for a lot of apps that are used by actual people, dark interfaces are not a good thing.
Dark Mode also ‘doubles’ the workload on developers and designers. It causes apps to split their resources between light and dark appearances ultimately compromising the beauty of both. I think many apps still look bad with just one colour scheme to consider, following the transition away from skeuomorphism. I believe there’s a lot more work to be done with what we have today before thinking about supporting another branch of the design language. I would be more in favour of a dark iOS if it was the new base UI, replacing the iOS 7 white aesthetic completely.
Ignoring personal preferences and in spite of those issues, I do think Dark Mode has a good chance of happening in the iOS 10 cycle. For one thing, a lot of people want it. I asked on Twitter about iOS 10 feature requests and many people asked for Dark Mode. I’m not sure if people want it because it looks cool or because it helps reduce eye strain at night. If it’s the latter, Apple has already started addressing that issue with Night Shift and I can see them pushing that further with a fully-fledged night UI toggle.
Another factor in Dark Mode’s favour is the looming rumours for the 2017 iPhone which will include an OLED display for the first time. In general, OLED devices prefer dark user interfaces as the screens are incredibly power-efficient when showing black pixels. OLED contrast levels are also very good so dark themes simply look nicer. Apple Watch UI is black for this reason; back backgrounds are so dark it blends in with the bezel.
Bringing Dark Mode into the ecosystem ahead of the OLED iPhone release allows third-party apps to start the transition sooner which means. That being said, I find it difficult to believe that Dark Mode will be present in the iOS 10.0 builds announced next week. The feature could likely come with a later iOS 10.x update. I reckon we’ll have another significant iOS feature update in mid-season, just like iOS 9.3 this year.