As confirmed earlier, OnePlus has started to push the last Open Beta builds (based on OxygenOS) for OnePlus 3 and 3T smartphones. This OxygenOS based beta updates for these handsets will come as Open Beta 39 (OnePlus 3) and Open Beta 30 (OnePlus 3T). The company has also listed the release notes of this update on their forum page. As per the forum, the latest beta update brings improvements in Launcher, Camera and Multimedia section, we have updated in detail below.

Changelog of Open Beta 30/39 builds:

Launcher

Included new installs category in app drawer

Search tags option has been tweaked in app drawer

App List on hidden space and toolbox has been improved

Camera

Switching between rear and front camera has been optimized

Multimedia

Newly added scrub/seek functionality to AAC audio file timelines

This software update will be available for existing beta testers via OTA. After completed migrations on beta build, OnePlus will release the stable version for everyone. The weigh of this update for existing beta users will be in 66 MB (OP3T). If you want to join in beta program, download the custom ROM from forum and flash it on your device.

At the end of June, OnePlus has revealed the software maintenance schedule for the following devices - OnePlus 3/3T, OnePlus 5/5T and OnePlus 6. According to that the android or software version support for OnePlus 3/3T will end on November 2018, afterwards this device will only receive regular security  patches until November 2019.