Inspecting the Super Smash Bros. for Nintendo 3DS ROM data not only reveals features that will appear in the Wii U version, it also reveals features that don't yet exist in either version. I'm talking about DLC, of course. At the moment, Nintendo hasn't announced any DLC plans for the pair of all-star brawlers, but further inspection of Smash code yields evidence that the game can be expanded.
NeoGAF user PushDustin has examined both Japanese and English 3DS builds and found code that will allow players to load new characters and stages. In regards to Wii U-3DS connectivity, though we already know you'll be able to use the 3DS as a Wii U controller, PushDustin has discovered that the 3DS will also be key to controlling extra players in 8-player matches. Furthermore, there's a text prompt for "A Challenger Approaches!" — could this mean that you'll unlock new characters by connecting to the Wii U and downloading the data straight to your 3DS?
We should learn the truth behind at least some of these discoveries during the Super Smash Bros. for Wii U Nintendo Direct on October 23. Afterwards, sit tight until the game's release on November 21.