Some HTC One M7 variants appear to be getting a new OTA update. As for what's new, apparently not much. All we know is that it contains "important enhancements and bug fixes related to improving phone call experience," and that it isn't Lollipop.
The update is version 6.09.401.11, and weighs in at a fairly hefty 193.01 MB, so whatever was changed must involve some somewhat substantial code changes. The update also keeps the M7 on Android 4.4.3/KitKat. On the surface, this OTA appears to be for non-US models, so customers in the States probably shouldn't bother spamming that "check now" button.