The announcement was made on twitter by the HTC America president Jason Mackenzie.
But the May-end deadline is for carrier-specific HTC One models in the United States and Canada, Mackenzie noted in further replies. There is no word on when the UI will be made available internationally, but for the US update, the details of the update will be posted on HTC's US software update page.
Notably, the HTC One (M8) comes with Android 4.4.2 KitKat along with a brand new Sense 6 UI on top. The phone is powered by the Qualcomm Snapdragon 801 SoC coupled with 2GB of RAM and comes with a new duo rear camera setup.The HTC One (M8) is already available in several countries, however the India pricing and release is still awaited. Earlier, HTC told NDTV Gadgets that the India launch is likely to in the third week of April. It will be compatible with the LTE band used by Airtel and Reliance Jio for their 4G LTE networks in the country. However, the company said a software update may need to be rolled out to enable this compatibility.