If you use either the HTC One M7 or the HTC One M8 on T-mobile's network, then you might be poised to receive a software update soon if you haven't already gotten it. For this years HTC flagship owners, the HTC One M8 will be getting an update that will enable the power saving mode which should relieve a little bit of stress on your battery and allow you to get more life out of it during the day. HTC One M7 owners however will be getting an update that brings their Sense UI experience forward into the modern age, as the update contains the evolution to Sense 6. That means updated Blink Feed as well as a few UI changes and tweaks like the updated camera and gallery.
When it comes to the HTC M7, the Sense 6 update is massive so make sure you have plenty of battery life to let the update persist and do its thing. You also want to make sure that you have enough space to allow the update to complete. While it likely won't be hard for most users as they probably have more than enough space to begin with, the update is 695MB total which is no small size. It's also said that users of the M7 who get the update should see the power saving mode in addition to Sense 6.
For those using the HTC One M8, the update should be quite a bit smaller as it only includes the power saving mode feature and likely a few bug fixes like most updates. In this case the fixes should be centered around audio and WiFi performance. The update is slated to start hitting phones today which if true means that it's being pushed out today by T-mobile, but it does not mean that all users will receive the update before days end. The reality is that it will probably take till mid week before most or all users on either phone see the updates come to their device. You'll want to be scanning your status bar for the software update icon to hit, but you can also manually check for the update on your own by navigating to the settings menu and tapping software updates from the about phone section.