Mitchel Broussard, writing for MacRumors:
The internals of both devices will see a notable overhaul in their Bluetooth capabilities, with each device getting a bump from Bluetooth 2.1 to Bluetooth 4.2. The upgrade will bring about Apple accessories that should see a noticeable increase in battery life and more robust communication between the input devices and the main computer.
Also of note is the inclusion of integrated lithium battery packs, which users will have to charge instead of the swapping in traditional AA batteries as seen in the current generation of the Magic Mouse and Apple wireless keyboard.
I don’t use Apple’s wireless keyboard very often anymore — instead most of my typing takes place on a MacBook Air or iPad. But I recently found myself in front of a friend’s iMac and I was amazed at how uncomfortable the keyboard felt to me.
Maybe it’s because I’ve grown accustomed to the flatter feel of typing on my MacBook, but it left me wishing that Apple could find a way to get rid of the battery compartment — allowing their standalone keyboards to feel more like their laptop keyboards. And I’m glad they seem to have been thinking along the same lines.