Just recently, Nintendo made available a new system update (5.1.0.U) that will allow players to transfer the saved content from one Wii U console to another. The new “System Transfer” feature, located in System Settings, will make this new option possible. Of course, before making the transfer, both consoles must be updated first.
Also included in the latest update, the console will give users the choice to use Wii Remotes, Wii U Pro Controllers, or Classic Controllers, with the Nintendo eShop, and improvements for system stability and other adjustments.
Except for the Internet, TV and TV Remote settings, all games, add-ons, apps and other settings will be transferable to the target Wii U console.
[Source]: Nintendo: Wii U System and Feature Updates [http://en-americas-support.nintendo.com/app/answers/detail/a_id/3070/p/431]; What Is and What Is Not Transferrfed During a Wii U to Wii U System Transfer [http://en-americas-support.nintendo.com/app/answers/detail/a_id/8989]; Wii U to Wii U System Transfer FAQ and Overview [http://en-americas-support.nintendo.com/app/answers/detail/a_id/8983/p/431/session/L2F2LzEvdGltZS8xNDA1OTkyNTA1L3NpZC82cDZmX1RabA%3D%3D].