Microsoft Ribbon on the HUD to Apple Touchbar on the Keyboard. I think this was a natural transition since it is more customizable and baked into more applications. The mobile/social UIs have created an opportunity for Apple to make a more modular interface that goes beyond the screen, or at least extends the screen onto the keyboard.

This also allows Apple to avoid making the primary screen a touchscreen since they ergonomics don't make sense with the current form factors. Also, by not making the entire keyboard surface touch it ensures the primary typing experience with haptic feedback stays intact.