Asus Transformer Prime is now receiving firmware update to version 9.4.2.21 OTA as they announced yesterday. This update brings new features such as Lockscreen Notification control, ASUS Vibe 2.0, Ethernet support via USB adapters and more. Sadly, there is no Face unlock feature in this update.
Additionally, this update has a new browser option that lets you save the websites to preferred browser setting, Tablet (default) or Desktop and option to lock the taskbar by pressing the center and sliding from left to right.
The new update is now rolling out OTA in UK and the US with other countries to follow soon.
Source: Asus UK (Facebook)