This is something we’ve been asking for for a while now, but good to see Nintendo being progressive: your Wii U and 3DS will work off a unified account.
A report over at Games Industry confirms that players will likely be able to transfer data – including games – back and forth between the Wii U and 3DS. This is something we’ve been able to do with the PlayStation 3 and PSP/ Vita, as well as Apple products for a while, but Nintendo downloadable content had previously been locked to a system (aside from a horrible transfer tool from DSi to 3DS and 3DS to 3DS).
So yep, buy that Wii U safe in the knowledge that your content will finally be able to be transferred to a new model painlessly. About time.