As part of the latest Nintendo Direct, Nintendo just announced that Mario Kart 8's world-colliding DLC is coming out next week.
It's coming out on November 13, specifically. It includes Link, Tanooki Mario, and Cat Peach as playable characters and eight new levels, including ones based on F-Zero and classic Mario Karts.
It will run you $US8, or you can grab Mario Kart 8 DLC packs one and two for $US12. DLC pack two, which includes Animal Crossing-themed stuff, will be out in May 2015.