Nintendo, Microsoft, and Mojang are teaming up to bring a free update to the the the Minecraft: Wii U Edition that includes new Super Mario themed skins, a Super Mario-themed pre-made world and a set of Super Mario music and item textures. The retail version of the game will be released for $29.99 on June 17th and will include the Super Mario Mash-Up pack on the disc. Also included will be many of the most popular previously released content packs at no extra charge.
Source: https://www.bleepingcomputer.com/news/gaming/super-mario-mash-up-pack-coming-for-free-to-minecraft-wii-u/