It is super rare for an OEM to support a nearly three-year-old device with pretty much anything other than quarterly software upgrades. OnePlus has always been known for its top-notch software support for their devices. The company had promised Android Pie for the OnePlus 3 and 3T and today, the update appears to be rolling out. The update is now available via a Community Beta. Here's the changelog:

SystemUpdated system to Android™ 9 Pie™Brand new UI for Android PieUpdated Android security patch to 2019.4Do Not Disturb modeNew Do Not Disturb mode with adjustable settingsNew Gaming mode 3.0Added text notification modeAdded notification for 3rd party callsPhoneDeep integration with Google DuoCameraIntegrated Google Lens mode

The update brings Gaming Mode 3.0 along with all standard Android Pie features. The Phone and Camera apps are also getting some new additions, with Duo and Lens integrations, respectively. To install the update, head into your Settings -> System Update -> Cog icon. Tap "Local update" and select the file you downloaded. The update process should start then and it may take several minutes for the software to load.

Once the process is complete, reboot your device and you should be running Android Pie. This method is only applicable to users who are running a stable build of Android on their device. People running a beta version of OxygenOS will have to sideload the update via recovery/ADB, and that involves a complete wipe of the device. You can download the build for the OnePlus 3 and OnePlus 3T using the links. It is still a long time before three major software upgrades become a norm in the Android world. But, if companies such as Google and OnePlus set the precedent, hopefully, others will follow suit.

News Source: OnePlus