That's a weird tweet -- UIApplication and UIViewController have not been deprecated. Maybe he means the way they changed how orientation is handled with ViewControllers. That certainly played havoc with my own apps. But that happened in the change from 7 -> 8, it's been around since 8.0.
If you don't mind me asking, what changed in 8.3 that could break a game so badly? I know that the move from 7->8 did some disastrous things to my apps because the ViewControllers' view bounds are orientation-based now. But moving from just 8.2 to 8.3 caused a show-stopping bug? Bob