Now when Apple is to phase out the UDID, what will happen to Unity’s class iPhoneSettings.uniqueIdentifier?
Are we better off generating our own unique identifier for each game (some md5 string at first boot of the app)?
I only worked once with an Android phone, so i don't even know what uniqueIdentifier has returned by this (old) property, but i guess it's the phone's unique identifier which identifies the device.
If that's what it was good for, it has been moved to a more general place. Specifically here: SystemInfo.deviceUniqueIdentifier which should return the UDID (unique device identifier)
I'm not sure what this property will return in future builds since, like you said, iOS has removed the possibility to read the UDID of the device.