An Android Oreo Open Beta program for OnePlus' latest smartphone 5T looks imminent. The company's German arm sent out a tweet yesterday, suggesting this.
When translated, the tweet reads:
Christmas is over, but we still have a present for you! ;) How about the Open Beta for Android Oreo on the # OnePlus5T!
So the tweet clearly indicates that an Open Beta will be announced this year. There's still no information on the final release, but that shouldn't take long as well if everything goes fine in beta testing.