Earlier today, Google Chairman Eric Schmidt was asked when Google Now would be available on the iPhone. He responded by saying, "You'll need to discuss that with Apple," which appeared to indicate they had submitted the app to Apple for approval.
However, Apple has now told CNET that the Google Now application was never submitted to its App Store for approval.
It's unclear exactly what's going on here; however, perhaps it's possible that Apple told Google they wouldn't approve the update if submitted so it never was. This leaked video does appear to suggest that Google is ready to launch.