Perhaps Apple, Microsoft etc. should consider using Bittorrent as a way of distributing their updates? If ISPs were to run their own Bittorrent servers (with appropriate restrictions, see below), this would then create an instant CDN, with no need to define any other protocols or pay any third parties.
They should do it like the game vendors. You are able to preload the game but it will only run on the day it is released. But, you still have to make sure not all your customers fetch the content at the same time with full speed. And what about thouse who just own a phone and no computer with iTunes? These customers will prefer to download over wifi as fast as possible to get the upgrade done. Preloading over anything other than wifi is way to expensive. Someone mentioned Win8/8.1 and Upgrades, there will also be OSX Mavericks quite soon. Fewer devices but way more content ... Access is sold by bandwith, so there will be oversubscrition. Sell it by traffic and all thouse iPhone users will walk to the neares Apple store to buy an USB stick with the upgrade since its cheaper than downloading it. rm