Part of me will be surprised if the game's aesthetic remains the same as those early screens. The visuals are clearly a port of the Wii game, just in high definition. The screens seem to speak more to concept than final product, especially given how much more powerful the Wii U is over the Wii.
At the same time, this might really depend on how much Nintendo wants to spend on the game (and instead save money for their inevitable 3D Mario). Perhaps more importantly, we don't know how the Mii aesthetic will change on the Wii U. With the console's power, there's no reason that the models cannot be better looking, more in line with the 360's avatar quality; but Nintendo might not want to create much disparity between the Wii U and 3DS Miis. Consequently, they might leave the visuals roughly the same in order to enforce consistency.
June can't come soon enough.