Just yesterday, HTC announced that it would bring its new Eye Experience to existing One devices via a future update, and some people in Europe are already seeing the enhancements come to their devices. The goods are bundled up with Android 4.4.4, and they're bumping users up from version 2.22.401.5 to 3.28.401.6.
A full download is available over at the XDA Developers forum for anyone who wants to rush in and get their hands dirty. The OTA comes in at 252MB.
This video provides a look at the update and some of the new things introduced by the HTC Eye Experience. It's not in English, so I haven't been able to gleam any other information from it, but that's no reason not to take a look.