Samsung's Galaxy J7 Prime, and Galaxy Tab E 8.0 are going to receive the Android 8.0 Oreo update on T-Mobile. Both phone launched last year with Android 7 Nougat on board.
The Galaxy J7 Prime and Tab E are joining the waiting line for Android 8.0 Oreo update, including the Note 8, Galaxy S8 series and S7 series available on T-Mobile.
T-Mobile doesn't have a release date for its upcoming Android 8.0 Oreo updates.
Source: T-Mobile Support (Galaxy J7 Prime, Galaxy Tab E)