Currently, the HTC One (M8) and its predecessor HTC One (M7) have been updated to Android 4.4.2 (KitKat) with Sense 6.0. According to a leaked roadmap from Llabtoofer, Android 4.4.4 will roll out to the said devices from July to August and may skip Android 4.4.3. The leaked roadmap also reveals that Android 4.4.4 will be rolling out to the One Mini 2 and One E8 from August to September.
As for Android L, HTC did announce that the latest version of Android will roll out to the M8 and M7 within 90 days after Google releases the final version, but failed to announce when exactly to expect the rollout of the update. The leaked roadmap reveals that Android L is under “evaluation” and may roll out from October to December.
Of course, since Llabtoofer’s roadmap is unofficial, take this with a pinch of salt.
Keep it here at Phones LTD for further updates.