Night mode was brought to Android Twitter last month, so it was only a matter of time before it landed on the iPhone. I believe Apple could take this one step further though. I would like to see night mode an OS level option. With apps having alternative themes for night mode that are triggered as you toggle Night Mode in the OS. This would be far simpler than toggling it in a per app basis. I would say it’s likely Apple may introduce this in 2017, to pair with the OLED screen, simple because it will improve battery life.
http://www.theverge.com/2016/8/13/12465362/twitter-night-mode-iphone-apple-ios