Even though the 3DS introduced SpotPass for the first time, the concept stems from an earlier Nintendo system. The Wii made use of a similar idea with WiiConnect24, but it was severely underutilized compared to SpotPass.
So what’s the point of talking about this? Now that the “downloading while you sleep” feature has been realized with the 3DS – for the most part anyway – there’s a chance that the Wii U could be supporting the functionality.
As shown in the Wii U development kit image above, there appears to be a setting for “Spot Pass setting”. That alone isn’t enough to confirm anything (especially since we can’t confirm the validity of the photo), but it wouldn’t be too surprising to see a form of SpotPass support for Wii U.