How to get the free iWork and iLife for iOS for existing users?

Apple said they are free for new devices. What if you are an existing user that don't want to buy a new device? I check the app store on iOS6 and they are still for paid. From the keynote, it seems that one way to do it is to wipe the iDevice once iOS7 is out and presumably you would be greeted with the free download screen. Why won't Apple just set those apps to free in the app store?

Anybody with the GM have ideas? I think this was mentioned by somebody even on the earlier beta.