"After the Nintendo 3DS system update, users can register their Nintendo Network ID for Wii U on their Nintendo 3DS systems and combine Nintendo eShop account balances. This will enable them to purchase Wii U software using the remaining balance on their Nintendo 3DS eShop accounts, and vice versa. Nintendo 3DS owners who do not own a Wii U system can also create their own Nintendo Network ID for the first time.
This system update will also mark the beginning of Miiverse support on Nintendo 3DS. With a Nintendo Network ID and a wireless Internet connection, users will be able to connect with players around the world to share their experiences and game tips through Miiverse on Nintendo 3DS. For more information and notices from Nintendo about the system update, visit http://www.nintendo.com/3ds/nnid.”