ASUS has announced as now provided to Android 4.4 for the slightly older PadFone 2 to download the update. The software update is, however, not via OTA sent directly to your smartphone, but must be manually installed.3146ASUS Padfone 2 Hands-On
The update to Android 4.4 KitKat for the presented in 2012 ASUS PadFone 2 brings not only the usual KitKat features with it, but also the new ZenUI surface which holds a lot of additional features and was introduced a few weeks ago.
As mentioned, the firmware update must be installed manually on your device because it at least thus far does not constitute an OTA update. Fits to ASUS has released a guide. The necessary files for installation can be found here.