Super Smash Bros. Creator Masahiro Sakurai has posted a new screenshot for the 3DS version of the upcoming Super Smash Bros. game on the Miiverse, along with the following comment:
"Pic of the day. Where am I......?? To be clear, the new Super Smash Bros. games does not feature a story mode like The Subspace Emissary."
CVG are speculating that this is a strong hint towards the game including a single player adventure mode, distinct from the Subspace Emissary. If so, it's not a stretch to imagine that the 3DS and Wii U versions of the game will be receiving their own separate single player modes.