HTC has gotten quite into the habit of updating its built-in apps through the Play Store, and that's a good thing. It means you don't have to wait on full system updates to get new features. Now that extends to the stock HTC lock screen, which has just been added to the Play Store.
The features listed on the Play Store page are not very detailed—you can swipe right to BlinkFeed and left to the widget home panels. So no major changes just yet, but now HTC will be able to update this component quickly going forward. The only addition is apparently a new mechanism to prevent you from accidentally triggering factory reset.
Note that installation will require you to reboot your phone, and a few users have reported bootloops afterward. However, that seems to be the exception rather than the rule.