Some time ago, the Android OEM OnePlus committed itsefl to provide an update to Android 9.0 (Pie) for its 2016 flagships, the 3 and 3T. However, it may have fallen behind in these plans recently. Now, a potentially important piece of evidence that the company has at least started on this project has surfaced.
https://www.notebookcheck.net/OnePlus-could-have-started-work-on-Pie-for-the-3-3T.410836.0.html