Masahiro Sakurai of Nintendo has confirmed that Super Smash Bros on Wii U and 3DS won’t feature a traditional story mode, like Brawl did. It will feature a single-player campaign of some kind though. He said recently:
As you already know, Smash Bros. has a large number of different characters, which were entitled to their own cutscenes in the story Mode. These were supposed to be rewards for players finishing this mode with each of the characters.
I think it was something fun for the players, but at the same time, all the cutscenes finally found themselves on the internet. Players watched them online, which was not really sticking with what we had originally planned. It is for this reason that we are not going to do something similar this time.
Nevertheless, we expect well introduce new characters with cinematics of introduction, as we already did for the villagers of Animal Crossing Mega Man or even the coach WiiFit. We have several ongoing collaborations to propose several cutscenes of this kind there.
Honestly this reasoning makes sense to me. The only reason I played the subspace campaign of Brawl was to unlock all the characters. No one buys Smash Bros for the story mode, which only Brawl had and even then it was only used to introduce new characters.
The game will still have a single player mode that resembles a story mode but at least for now Sakurai is saying it won’t be anything like the story mode in Brawl. No more subspace for you!Super Smash Bros 4 story mode is changed so that players don't 'watch cutscenes online',