Developers aren’t the only ones who have to test new builds of iOS. Carriers have to check it out, too. According to some reports, carriers are getting their builds of iOS 7 beta 3 on July 8.
The folks who make this claim also knew the release of iOS 7 beta 2, so they have been accurate in the past.
As MaCNN points out, the first beta released earlier this month. The second, exactly two weeks after. If the third releases on July 8th, this is an indication that Apple is keeping up with a strict beta release schedule.
We should see iOS 7 release to the public sometime this fall, alongside any new handsets or iOS devices Apple plans to unveil.