WPCentral reports that the official RTM build of Mango (build 7720) has been leaked on the XDA forums
Yup, this story is still developing but it looks to be the case. A poster by the name of longshot442 has posted a 404MB file which contains the official RTM build of Mango aka build 7720.Windows Phone Mango Build 7720 leaked
Evidently, users are able to flash devices ranging from NoDo, 7661 or build 7712 up to 7720. You do not need to restore from your backup, but instead can update directly.
