The latest beta of Apple's upcoming iOS 8 is apparently only for carrier testing, giving the strongest indication yet that its release is imminent.
BGR reports that the latest beta, version 8.0 (12A363d) was for carriers only and not developers because it's apparently incredibly close to the final golden master version.
Carriers apparently have until September 5th to accept the latest build, although there may be problems there owing to YouTube/Safari compatibility issues. As you might expect this close to release, the notes specify bugfixes rather than genuine new features within the operating system.
A date of the 5th wouldn't make it impossible for Apple to run a surprise announce of iOS 8 on the 9th of September in the States, although it would be cutting it very fine indeed.