Reports of the dedicated YouTube app gone missing on iOS 6 beta 4 were first spotted on 9to5mac. Speculations around that had to do with Apple breaking all ties possible with Google, which started with their own mapping solution to break the dependence on Google Maps.
Now a report from The Verge states that Apple's license of YouTube has expired, which means that they won't renew it and will remove it from iOS. Read Apple's statement to The Verge below:
Our license to include the YouTube app in iOS has ended, customers can use YouTube in the Safari browser and Google is working on a new YouTube app to be on the App Store.
The same report states that Gogole is working on an app of their own to submit to the App Store soon.
Apple created YouTube app has been part of iOS since its first version in 2007, alongside the Google Maps app, which is not going to be available with iOS 6.