The Galaxy S9 and S9+ have been eligible for beta versions of One UI 2.0, Samsung's custom version of Android 10, for months now. The arrival of Android 10 on the Galaxy Note 9 brought hope to the idea of Samsung honouring its January release schedule for the S9 series too, but that no longer appears to be the case.
https://www.notebookcheck.net/Samsung-fuels-theories-that-the-Galaxy-S9-and-S9-Plus-have-had-their-One-UI-2-0-and-Android-10-updates-rescheduled.451717.0.html