A lot of OnePlus 2 owners have felt burned due to the lack of OTA updates that OnePlus has pushed out. For a while, owners of these devices were told that the OnePlus 2 was eventually going to be receiving an official update to Android 7.0 Nougat. That unfortunately turned out not to be the case, thus making the last official build of OxygenOS for the device to be based on Android 6.0 Marshmallow. Thankfully, the device still has quite the developer support on our forums, and developers have just released an early build of LineageOS 15 based on Android 8.0 Oreo for the device.
OnePlus promises they'll have better long-term software support for the OnePlus 3 and the OnePlus 3T since they have organized their software development division. We'll have to wait and see how that turns out, but users of those devices should take solace in the fact that the OnePlus custom development community has always been strong, so even if OnePlus is unable to continue providing support, members of the XDA forums will be there to fill the gaps. Though we don't yet have official builds of LineageOS 15 for any device right now, community developers are building ROMs based on what's already there in the gerrit for a number of devices.
The latest to get its first taste of Android Oreo via LineageOS 15 is the OnePlus 2, and this build is possible thanks to XDA Recognized Contributor Shreesha.Murthy (as well as the entire LineageOS team). This initial release was made available yesterday and it has already been updated to revision 3. As usual with these early builds, this is to be considered an alpha and there are some bugs you should be aware of. A lot of stuff does work though, including RIL, WiFi, Bluetooth, hotspot, fingerprint scanner, VoLTE, and the sensors (GPS etc.).
However, there are some things that currently do not work and are still being debugged at this time. As of writing this, that includes the camera, alert slider, offline gestures, and possibly more. With an early build like this, it's impossible for one developer to know all of the bugs which are present. So if you come across any then please be sure to report it (and include logs) in the thread linked below.