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I don't think it was specifically mentioned. Engadget currently has this to say in one of their articles: "It's not yet clear if it will be available for all iPhones or just the iPhone 4S -- we'll bring you more as we get it."
 
No, they mentioned it as a feature of iPhone 4S, not as a feature of iOS5. They need something that's unique to the new iPhone. Jailbreakers probably will figure out how to enable it though.
 
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