It's not entirely clear if this is a worldwide release, or if it's limited to specific regions. Based on some Reddit posts, though, it looks like Samsung has started the rollout in Europe and some parts of Asia: users from Italy, Switzerland, Greece and the UAE reported getting the new OS on their phones. Aside from location, one common factor among several posters who reported getting the update is that they have international versions of the Galaxy S9 and S9+. Some of them also said they received the update after installing their phones' December security patch. Those who still haven't gotten it may want to check out Software Update under Settings and downloading the security patch if they haven't yet.