T-Mobileís @askdes has confirmed via Twitter that the T-Mobile variants of the Samsung Galaxy S6 and Galaxy S6 Edge will be receiving their Android Nougat update starting this week. The rollout will begin and assumingly take a week or so to completely roll out.
The update will bring Nougatís added features like enhanced notifications and improved permissions for applications. You also get improved system optimization and battery improvements. Nougat will definitely be an update of at least 1GB in size, so start transferring your photos to an external source or cloud service.
Another option for updating your S6 is to download and Install Smart Switch on your PC or Mac. When your S6 is plugged in, Smart Switch should prompt you to update once the OTA becomes available.