It will be several GB. And you cannot do OTA software updates on cellular network, you've never been able to and you can't now. It requires you to be connected to wifi, so you will have to wait until you get home.
Yes, the public release will be available as an OTA update for users currently on iOS 6. It is only the pre-release GM that is not available OTA. The public release will be. (This was the case with iOS 6.)
If they do an OTA update for iOS 6 to 7. It's roughly going to be 900MB+ you won't be able to use LTE to update as I think the cap for carriers is 50MB. The GM is 1.1GB and 1.2GB depending on you model device.
If they do an OTA update for iOS 6 to 7. It's roughly going to be 900MB+ you won't be able to use LTE to update as I think the cap for carriers is 50MB. The GM is 1.1GB and 1.2GB depending on you model device.