After pushing the Android Pie for Galaxy Note9 and S9, T-Mobile has moved further and started testing the Galaxy S8, S8+, and Note8 for the Android 9.0 Pie update, that'll soon begin to roll out to its consumers.
According to the support page of T-Mobile, Galaxy S8, S8+, Note8 are currently in testing phase for Android 9.0 Pie update. At this stage, the device goes through a certified testing process to find and fix various bugs and issues in the developed build.
T-Mobile's update program consist of three stages including Development, Testing and Complete (Rollout). Now when the company has put the new phones in test stage we can expect the users of S8, S8+ and Note8 on T-Mobile can receive the Pie update anytime soon.
While T-Mobile has started testing Pie update for these phones, it can be expected that other mobile carriers in the US may also be working for their S8 and Note8 and will roll out the update altogether.