That's right, Sprint has made it official: the rollout for the Lollipop update for the HTC One (M8) starts today. As with all such over-the-air releases though, it may of course take a few (or more) days until it reaches all the devices out there. Rest assured that it is on its way, however.
It looks like the initial rollout time frame was set for next week, but for whatever reason Sprint decided to push things forward, which is definitely good news for owners of the One.
Your phone will notify you when it's ready to download and install the update. If it hasn't done so already, you can always manually check by going to Settings > System updates > HTC software update, and then tapping on Check now.
After applying the update, you'll be running build 4.20.651.10. Aside from moving the base to Android 5.0 Lollipop, this new software also removes the Lumen Toolbar.