Apple has offered up iOS 8 beta 4 to developers two weeks after the third beta, which came two weeks after the second. See a pattern?
The company is rolling out a steady stream of test code for developers to build their apps upon before the public release this fall, which will almost certainly coincide with a new iPhone version.
iOS 8 promises a number of important new user-facing features, including Extensions like custom keyboards, Continuity for handing off functions between iOS and OS X devices, actionable notifications, as well as a new focus on health.
Apple will be reporting its fiscal Q3 2014 earnings on July 22nd, so stay tuned.