Android tablet lovers have fewer and fewer options nowadays, and it doesn't help that these tablets often get relegated to the back of the update priority list. Samsung just recently began rolling out Android 8.0 Oreo to its Galaxy Tab S3, the Huawei MediaPad M5 ships with Oreo too, but Lenovo's most recent tablets, the Tab4 series, are still on Nougat 7.1. There's hope though, if you're very patient.
Lenovo is now saying that the Tab4 8" (TB-8504F, TB-8504X), 8" Plus (TB-8704F, TB-8704X), and 10" (TB-X304F, TB-X304L, TB-X304X) will be upgraded from Nougat 7.1 straight to Oreo 8.1. You will need to wait until November of 2018 for the OTA to roll out, if all goes to plan. There's no word on the Tab4 10" Plus yet, so if you own that model, you may need to exercise even more patience.