Just a few hours after Google announced in the I/O conference that they will be releasing Android “L” (early guesses put it at either Lollipop or Lime) later this year, HTC already posted on their blog that they are committed to quickly upgrading their flagship One (M8) and ex-flagship One (M7) as soon as it is actually possible. They are committing to update the smartphones 90 days after Google turns over the final software to them.
HTC has always claimed that they are one of the earliest OEMs to roll out Android updates to their devices, although if there are delays to reaching the actual customers, they put the blame on the carriers. Nevertheless, they have expressed their commitment to already start on what they call their “Pre-Evaluation Phase” in which they are already looking at the components even before they enter the Phase 0 of updating once the official software has been released to OEMs and chipset manufacturers.
Although Android "L" has been revamped with new user interface design and color scheme, named the Material design, you might not see the Material design in the updated HTC One software. Manufacturers like HTC usually applies its own design together with the Sense UI.
HTC wants to be transparent when it comes to updating their customers as to where they are in the process. They have a software updates page that you can check out.