Putting the kart before the horse
Nintendo would like you to buy Mario Kart 8. Maybe even its Wii U bundle. And for doing so, you shall be rewarded handsomely. Those who register their Mario Kart 8 on Club Nintendo before July 31 will get a copy of Wind Waker HD for free.
If you already own Wind Waker HD because you are talented and beautiful and well-liked, I suppose you could choose between one of the other three free options: Pikmin 3 (more like Pikmin Free!!!), Wii Party U, and New Super Mario Bros U.