The Nintendo Direct today announced that not only will we be getting the new characters from Legends on Wii U, but that there is a new character coming (Bird girl from Wind Waker) and there will be 4 all new DLC packs in a dedicated season pass, so I assume that means even more characters. SO MUCH TO DO IN THIS GAME!
*EDIT*
Okay, apparently the season pass might be only for Legends. If that brings more new characters, I don't know if they will be left to the 3DS only. I hope not. Was kinda wanting that new season pass to be on Wii U since I'm not really going to play the 3DS version much.