OxygenOS Open Beta 39 for the OnePlus 3 and Open Beta 30 for the OnePlus 3T

OnePlus Today Released New OxygenOS Open Beta Update For OnePlus 3 and 3T,this open beta updates brings few new features and fixes.last week on 4th July oneplus rolled out update for Oneplus 5/5T.

Release Notes
Launcher
Improved search tags in App drawer
Added "New installs" category tag in App drawer
Improved app list for hidden space and toolbox.
Camera
Optimized switching between front and rear camera.
Multimedia
Added capability to scrub/seek through AAC audio file timelines.

it is worth nothing that  oneplus 3 and 3T will not receive any major android os update,these two devices will only receive regular android security patch updates from oneplus, currently these update is bing rolleing out in batches it will take time to hit your oneplus device or you can manually check for update  

Source