IOS – What’s the current state of delta updates for iOS apps? Were they ever promised? If not, any word from Apple on if it will come

I'm quite sure that I read, in more than one place, that one of the features of iOS 5 was to be delta updates for apps. However, the massive download that was required for an update to Infinity Blade II (a great example of just the sort of app delta updates would be tremendously useful for) suggests to me that its update was done the old way, by a complete download of the entire new version of the app.

To make perfectly clear, I'm asking about when and if we can expect delta updates for iOS apps. Mac programs in the Mac App Store do not interest me. Another thing that might have confused reporting in the run-up to the release of iOS 5 is the fact that over the air updates for iOS itself are delta updates. Could it be that Apple never even promised delta updates for apps, and the press simply got these two things confused?

Edited to add:
Since my original question wasn't clear, I'll try again. I know that right now, there are no iOS app delta updates. What I'm curious about:

• Had Apple ever explicitly told developers or the press that they would be doable in iOS 5?
• If so, does anyone know why it hasn't happened?
• If not, has anyone heard if it's being worked on for the future?