Android Oreo comes with numerous enhancements over Android Nougat, such as faster booting, new Settings and Quick-Settings UI, Picture in Picture (PIP), Adaptive icons, Autofill, Notification timeout, Nokia might also add several new features to the latest software update. Android 8.0 Oreo update for the Nokia 6 would also feature the latest Security Patch.
If you own a Nokia 6, you'll have to sign up for HMD's beta labs program, and enter your device details. Once your phone is enrolled, you'll receive beta builds as and when they're available.
Assuming this beta test works out OK for testers, we nufgr see stable Oreo build sometime early next year.