Update: We have a vague description on what the update does.
Update: According to Nintendo's website the update (version 2.1.0 U) further improves system stability and causes other minor adjustments to enhance the user experience
A new firmware update is now available for download onto your Wii U.
The update has just become available and comes in at a size of 593 megabytes. Once our updates have finished installing, we will be able to report on what exactly it contains.The update, given its size, may finally unlock Nintendo TVii functionality.
Check back with Nintendo World Report for more information on this Wii U firmware update.