Apple released iOS 5 beta 4 today, along with iTunes 10.5 beta 4 and Xcode 4.2 Developer Preview 4, to developers. The most significant part of this news is that Apple has enabled the ability to update to iOS 5 beta 4 OTA for developers on iOS 5 beta 3 (confirmed working on both Wi-Fi and 3G). As always, a matching beta version of iTunes 10.5 is required to sync with the newest iOS beta, and both betas are strictly meant for developers only.
Note that if you’re a developer wanting to attempt an OTA update, it will fail if you happen to be jailbroken because a check is performed to ensure that /Applications is a real directory on the iDevice (confirmed by iPhone Dev Team member MuscleNerd), which it is not when jailbroken. The OTA update also currently deletes all photos on the iDevice, so you’ll have to re-sync with iTunes to get them back after the update is performed.
As the beta releases continue, bugs continue to be worked out and new features are being released by Apple and tested by developers before the software is ready for the public this upcoming fall.