As Google appears close to bring the Android 5.0 to its Nexus devices in the first week of November, HTC has already confirmed to its users that the first round of devices including the HTC M8 will receive the update to Android L within a period of three months when the final version of Android L is released. It looks like the update will also bring an update to the Android skin on HTC devices with Sense 7, along with Android 5.0.
The first screenshots of the update gives us a peek at the battery stat screen as well as the device information screen. It is worth noting that the top status bar and the soft buttons on the device are exactly the way they were on Sense 6 and Android 4.4. The font definitely is the Android Lollipop one and you have the material design all across the board.
It is not clear whether there will be any other major changes such as those to the lockscreen or even to the widgets that are included as screenshots of those are not available. However, if the screenshots are already out, it means that the work is very much in progress and we may not have to even wait for the stipulated 90 day period for Android L and Sense 7 on HTC M8.