Time to put the thinking cap on. The SNES had the GameBoy Player allowing handheld games to be played on consoles. With GameCube, Nintendo did its biggest experimentation with console/handheld connectivity. Not only was there the GBA player to play Advance games on the console, there were link cables to use the GBA as a controller for some games notable Pac-Man VS, 4 Swords Adventures and Final Fantasy Chronicles. There were other minor uses of it. One could look at Pac-Man Vs and draw a sort of parallel to the Wii U with its controller screen giving a different perspective or giving that player a different ability /role compared to the other Wiimote players in a room like in some NintendoLand games. With the Wii, Nintendo backed away from connectivity and the DS hardly had much interaction with the Wii console for anything. With the 3DS and Wii U, that non-connectivity approach has continued for the most part aside from a rare exception. The biggest thing would be using it as a controller in Smash Wii U. However, the Wii U Gamepad sort of acts like a handheld device connected to your console.
Iwata put the handheld and console hardware teams together to get them to work together better no doubt in part because of the software / menu architecture needed these days to allow for sending out patches, emulating games through the VC, and accounts like the e-Shop or Miiverse. I think we've started seeing the effects of some of this through Miiverse being incorporated on both systems, Amiibo and NFC and a couple cross-buy game attempts. However, it's not nearly at the integration fans would like with GBA games non-existent on the 3DS e-Shop or the length it took SNES games to be released not to mention better cross-buy support of being able to buy an SNES game on 3DS but also download it to your Wii U account if you want or vice-verse instead of paying twice for the same game. That problem, however, may come from the fact that handheld and console development teams were separate before and didn't confer with the other team about how they could or should approach development to make that programming worth with both systems. We are still waiting to see the first console and or handheld be released under this new directive. Was this combining part of a plan and idea already in place and beginning for what the Wii U successor would be? Or has it created a new plan and bold new direction to attempt? (Yes, the NEW 3DS has come out and is technically the first handheld released under this combined development team but it clearly is still tied to the original 3DS design and architecture to be truly new or be considered a successor.)