In short: OnePlus announced today that it is rolling out Oxygen OS 9.0 to the OnePlus 6. This version of Oxygen OS is based on Android 9 Pie, which means that OnePlus 6 owners are currently getting the latest version of Android, and becoming one of the first smartphones to get the update. Outside of the Pixel lineup, the only smartphone that has gotten the update so far is the Essential PH-1, so this is definitely a good thing for OnePlus users. There are plenty of changes included in this update to Oxygen OS as well. This includes the new Android Pie UI, as well as Adaptive Battery support, the new gesture navigation from Android Pie, and other improvements. There is also a new Do Not Disturb mode that comes with adjustable settings. OnePlus is including Gaming mode 3.0 and this does come with the September 2018 security patch.
Background: OnePlus has been getting better at updating its smartphones, so it's not a huge surprise to see this update coming out so soon after Android Pie launched. Now this one is only for the OnePlus 6 so far, which is a bit unfortunate, but expected. Typically, the newest smartphones get updated before the older ones, and that actually comes down to Qualcomm, who needs to release the binaries for their chipsets to update these smartphones. And they always start with the newest, flagship chipsets first.
Impact: Those with a OnePlus 6 can head into the Settings and download the update. It may not download instantly, which in that case, you may need to wait a bit to get your update. As this is going to be a staged rollout as usual with updates. OnePlus notes that the update is being rolled out to a limited number of users today, to ensure there are no critical bugs in the update, before rolling out it out to all of its users.