In chronological order:
- Good ol’ laptop keyboard.
- Butterfly switch keyboard to reduce overall thickness of keyboard.
- Dynamic keys with Touch Bar. (where we are right now)
- Touch Bar with haptic feedback (Apple Taptic Engine?) to simulate key presses.
- Touch Bar with advanced haptic feedback to allow texture on buttons (and other controls).
- Entire keyboard replaced with OLED (or better) display with advanced haptic feedback technologies so it feels more or less the same as typing on a keyboard with butterfly switches. (This would probably appear on iPads first)
- (Maybe at some point there will be no difference between the display and the keyboard.)