Samsung has a long and complicated history with Android updates. It's reasonably fast with security patches, but that's not what most people use to measure success. It's the big updates that matter, and Samsung is often bringing up the rear when a new version of Android comes out. Here we are, six months after Oreo launcher, and Samsung is promising it'll be done updating the Galaxy S8 and Note 8 in a few more weeks.
The Oreo update has rolled out to some carrier versions of the Galaxy S8 (and S8+) and Note 8, but owners of the US unlocked version have been left hanging. Samsung makes the dubious claim that it takes longer to develop updates for unlocked phones because it has to test them on all carriers. Although, carriers have their own testing and certification procedure, and that seems to take most OEMs longer to complete. Thus, unlocked phones usually get updates faster. That holds true for Samsung's international unlocked phones. Kind of makes you wonder...
Whatever the reason for Samsung's tardiness, it says all versions of these phones will have the Oreo update in 2-3 weeks. That includes the US unlocked devices still languishing on Nougat. It does not have a firm date for the rollout, but the Oreo build is ready for final testing. Samsung says it'll post the news as soon as it releases the OTA.