Dedicated fans have rooted around in the files for Super Smash Bros. for Nintendo 3DS and found some interesting unused sounds.
The files, which feature the Smash Bros. announcer doing what he does best—announcing—suggest that other game modes might have been cut from the game, or could be available in the future in some form. The files hint at modes like "Boss Battle," "Tourney," and a very intriguing "8 Player Smash" as well as things like "Choose a Mii" and "Yellow Team."
While nothing is confirmed and all is conjecture at this point, several fans on sites like NeoGAF and Reddit hypothesize that these modes could be available in Super Smash Bros. for Wii U, and that the sound files exist to play through the 3DS speakers when using the 3DS as a controller for the Wii U game, similar to how certain sounds are played through the speaker on the Wii Remote. Another possibility is that these files refer to modes once planned for the game, but eventually left on the cutting room floor.
Only time will tell if these unused files refer to future content or modes cut from the game during development.