It seems that OnePlus 3/3T and OnePlus 5 will be the first non Google devices to get the Android 8.0 Oreo update. OnePlus has already started rolling out closed beta of Android 8.0 Oreo based OxygenOS for OnePlus 3. It is expected that Oreo based OxygenOS Open Beta (24/15) will be released by the end of this month (September) for OnePlus 3 and OnePlus 3T.
Popular OEMs like Samsung, LG, HTC, Sony, Asus, Nokia, etc have already announced Android 8.0 Oreo update for their flagshiped devices. Most devices will get the update by December or first quarter of 2018. Oreo is the biggest Android OS update with many new features and changes.
Comes to the Oneplus 3 Oreo update, the build is not yet ready for public test. Many major aspects of the OS are not working as expected, such as the NFC, WiFi, Hotspot, Bluetooth, etc. OnePlus is continue working on the update and the more refined public beta build probably will release by mid-September or end of the month.
Also note that, OnePlus may soon release OxygenOS Open Beta for OnePlus 5 too. It might be based on Android Oreo.
HydrogenOS (Chinese variants) beta users can also expect Android 8.0 Oreo based update even before the Oxygen OS update.
For your information, Android 8.0 Oreo is a smarter, faster and more powerful OS update. It features smart text selection, Instant apps, Picture in Picture, faster start up and app sign-in, Google Play Protect security Scan, notification channels, Adaptive Icons, fingerprint gestures and more. (Source – Androidpolice)