Take SpriteKit. It didn't exist until it was announced at WWDC 2013. Up until that point, the functionality offered by it was largely either hand-rolled by the developer, or achieved via framework (e.g., Cocos2D). I think Apple realized that they could capture more mind-share and confidence if they offered their own first-party framework offering.
Fast-forward a year later, and we have an enhanced SpriteKit (i.e., light sources, field forces, per-pixel physics, inverse kinematics), and of course the newly-announced SceneKit (3D scene rendering for casual games), Swift and Metal... all within a year!
With regard to Metal, Tim Sweeney had this to say after the Zen Garden app demo:
"There are thousands of objects being rendered here in a scene that we couldn't have dreamed of building, prior to Metal delivering a 10 fold increase in rendering efficiency. To have this level of graphics capability on iPhone and on iPad now is a stunning breakthrough. We're proud to have been a part of it. Of course, we'd love to share this with you, so as soon as iOS 8 is available, we'll be making Zen Garden available in the App Store for free."