It depends on the manufacturer and the carrier. In the particular case of the HTC One, there is a leaked 4.2.2 update (with Sense, not the Google edition) for

It depends on the manufacturer and the carrier. In the particular case of the HTC One, there is a leaked 4.2.2 update (with Sense, not the Google edition) for the international version of the phone that can be safely installed on carrier-specific versions. It will likely be available OTA in a few months.