Last summer Masahiro Sakurai stated that there'd be no cinematic story in the new Super Smash Bros. titles coming to the Wii U and 3DS. The reasoning was a little peculiar, as Sakurai-san said the following.
Unfortunately, the movie scenes we worked hard to create were uploaded onto the internet. You can only truly wow a player the first time he sees [a cutscene]. I felt if players saw the cutscenes outside of the game, they would no longer serve as rewards for playing the game, so I've decided against having them.
If there was any vagueness or risk of translation confusion at that time, the latest daily update on the Miiverse Director's Room for the game emphasizes that there'll be no story campaign in the style of Subspace Emissary from Super Smash Bros. Brawl, while also teasing a new 3DS stage.
Sakurai-san has promised that there'll be some form of single player campaign, so what would you like it to be? And in an equally important topic, what game or franchise do you think the new 3DS stage represents?