OnePlus has issued an over the air update (OxygenOS 4.1.7) to the OnePlus 3 and 3T with the August security patch and some fixes and optimizations. By request from Google the update will remove Hangouts from the core package in the case that it has never been updated so if you want to keep Hangouts on your OnePlus 3 or 3T you'd best update it on the Play Store prior to installing the update. Naturally you also get the chance to download it from the play store later on. Here's a full changelog: Improvements: Enhanced system fluidity Bluetooth optimizations Battery...
Source: http://www.gsmarena.com/update_for_the_oneplus_3_3t_brings_security_patch_removes_hangouts-news-26877.php