https://wccftech.com/today-in-android-oneplus-promises-android-p-for-3-3t-and-more/

Some time ago, OnePlus promised two years worth of major software updates and three months of security patches for all devices (except the OnePlus 2 and OnePlus X) much like Google. Two major OS upgrades are the industry and pretty much everyone follows it at this point. However, OnePlus has a surprise in store for OnePlus 3 and 3T users in the form of an Android P upgrade. Oreo was expected to be the last major update for the 2016 flagships. However, OnePlus 3/3T owners might have to wait a bit as they’re the last in line for the update as stated by OnePlus in a blog post.

The Android P update will be available on the OnePlus 6, OnePlus 5/T and OnePlus 3/3T, in this order. We will keep you all updated in the coming months.