After the success of the Wii wheel, (Mario Kart) balance board, (Wii Fit) and motion plus (Wii Sports Resort) I think it is safe to assume that Nintendo will release something new to help sell the Wii U. They have seen the success that add-ons can bring. Kinect helped the XB 360 a ton too. Nintendo even announced the "Vitality Sensor" which was canceled due to it not working as well as planned. (wonder what games they had planned?)

Anyway, my guess is as good as anyone else's but I'm going to go with haptic feedback support. Why? Back in 2011, if anyone remembers, rumors began stating that the Wii U would be called the "Feel" and would provide haptic feedback. This was obviously not true. The leaders of this type of tech "Vivitouch" and its "HD Feel" seem to be interested in bringing the tech to gamers. They've been to E3 for a few years now, showing off the "HD Feel" as well as a new headphone with "4D Sound". In 2012, it was rumored (again) that Nintendo would team up with vivitouch to include haptic feedback into the Gamepad, this was again untrue.

Fast forward to current time and the Wii U Gamepad (while cool IMO) still has yet to showcase something that gets the casuals excited. After some digging, I found this tweet from Vivitouch:

1.   Retweeted by ViviTouch

   Shoe ‏@DanShoeHsu  Dec 20

   Nintendo's holiday card:  http://holiday.nintendo.com/ 

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   2:31 PM - 20 Dec 2013 · Details

   This would seemingly tell us nothing. On the other hand, why would vivitouch care enough to retweet something Nintendo related if not involved with them in some way? Upon farther investigation, Nintendo's software development group #1 is responsible for only 2 series. Mario Kart & Nintendogs. In 2005, we had Mario Kart DS & Nintendogs release. In 2008, we had Mario Kart Wii & DSI sound. In 2011, it was Mario Kart 7 & ND + Cats. This year, we get Mario Kart 8...I'm expecting a Nintendogs U this holiday. 

   Imagine a Nintendogs game where you can feel the dog or cats fur on the Gamepad screen? It wouldn't be my cup of tea personally but I'm confident it'd help to put the Wii U on the map.

   or I could just be crazy. Anyway, what is your thinking about a possible add-on for the Wii U?

I hope it's a dick sucking add on for the gamepad.

I'd guess a Gamepad "Light". Smaller, lighter, more ergonomic and better looking. And with more battery life. I don't think we'll see anything else. Nintendo just released Wii Fit after a year's delay. Any other accessory probably will also be delayed a year, and they still have an uphill battle selling people on the original add-on, the Gamepad itself. Nintendo needs good ole fashioned software, and something that doesn't need anything extra to go with the Wii U.

As I said, I wouldn't buy the Nintendogs game if it happened but this is Nintendo. They were the add-on kings last gen, I expect something and pretty soon. Plus, maybe a Nintendogs U with haptic feedback could help sell the idea to the casual gamer? 

Either way, I agree. I'm hoping they just continue to release amazing games and if the Wii U sells piss poor, no loss for me. I just want great games

 Wii U shotgun... Now you can play Call of Duty like a true  man.

bazooka addon plox

they can disguise it as a wiimote cleaner. Yeah VR Glasses and a wiimote cleaner.. Sold out

Is that "gun" add on good to play shooters?

While they are at it they could rename the Wii U the Wii V. The Wii Vagina! I think the market is not ready for such an achievment though, Nintendo wouldn't be able to keep up with the demand in YEARS!

This turned into a joke thread pretty quick this time.

Ha Ha