"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Images of Apple Wireless Keyboard With Backlight Keys and Power Button Appear in Online Store [Updated]
Apple has not updated the product description for its wireless keyboard to match the new visualization, so it remains to be seen if this was simply a mistake or if the company will quietly refresh the keyboard in the near future. The old Apple Wireless Keyboard with no backlight keys and an eject key is still shown on the Apple Online Store in the United States, Canada, United Kingdom and other English-speaking countries.
The addition of a power button on the keyboard is interesting, given that Macs currently do not detect wireless keyboards until after booting. It could be speculated that the power button is for turning on or off the wireless keyboard itself, but additional photos reveal that the keyboard still has a power button on the side in its traditional spot. As such, the exact functionality of the key remains unknown.
Update Mar 24: Apple has removed images of the new Apple Wireless Keyboard with backlight keys and a power button on the Apple Online Store in Czech Republic and Hungary. Graphic renders of the current Apple Wireless Keyboard with no backlight controls and an eject key are now showing again.