Super Smash Bros. for Nintendo 3DS / Wii U

Super Smash Bros. for Nintendo 3DS and Super Smash Bros. for Wii U are the upcoming fourth installments of the Super Smash Bros. series being developed for the Nintendo 3DS and Wii U. Like previous games in the series, they are being developed by Sora Ltd. and directed by Sora Ltd. founder Masahiro Sakurai. On June 2012, it was announced that Sora Ltd. is working alongside Namco Bandai Games in developing the games. In the Nintendo Direct of E3 2013, Mega Man from the Mega Man series by Capcom was announced as the third guest character of the series, after Snake and Sonic from Super Smash Bros. Brawl. During a Q&A with Masahiro Sakurai, during 2013's E3, it was revealed that both games will not come out at the same time. It was also revealed previous characters may not make it due to the 3DS's space limitations.

Gameplay
Not much is known about the two versions currently. Final Smashes return from the previous installment in the series, Super Smash Bros. Brawl. Also, the "tripping" mechanic from the previous installment has been removed. It was also that the games cannot crossplay, but can send customized fighters to each version. It is unknown what/who these fighters are.

3DS version
The 3DS version has a cel-shaded graphical style, the characters being given outlines so that they can be seen better from a distance. The stages in this version are mostly based around handheld games.

Wii U version
The Wii U version has HD graphics along with stages mostly from console games.

Confirmed characters
According to Masahiro Sakurai, several returning characters may not make it to both versions due to space limitations on the 3DS.

Returning characters

 * Mario - Mario has been given brighter blue overalls with less detail compared to the overalls in Super Smash Bros. Brawl. His fireballs are bigger and have more detail.
 * Donkey Kong - Donkey Kong's fur looks slightly more detailed compared with his appearance in Brawl.
 * Link - Link is now based off his Legend of Zelda: Skyword Sword appearance.
 * Samus - Samus' appearance has been updated to reflect her appearance in Metroid: Other M.
 * Kirby
 * Fox - Fox's fur looks much more detailed than in his appearance in Brawl.
 * Pikachu - Pikachu appears to be slimmer than in the past installments.
 * Bowser - Bowser has a more upright stance and his running speed and attacks are faster.
 * Pit - Pit's appearance and moveset have been updated to reflect his appearance in Kid Icarus: Uprising.

Newcomers
(there are 6 more to be announced)
 * Villager
 * Mega Man
 * Wii Fit Trainer

Others

 * (Mega Man)

Stages
According to Masahiro Sakurai, the 3DS version of the game is going to feature more stages based on games for Nintendo handhelds, while the Wii U version is to feature more stages based on console titles.

Nintendo 3DS

 * A stage appearing similar to Battlefield from Super Smash Bros. Brawl.
 * Gerudo Valley, from The Legend of Zelda: Ocarina of Time (3D).
 * A stage taking place on the Spirit Train, based on The Legend of Zelda: Spirit Tracks.
 * Arena Ferox, from Fire Emblem: Awakening.
 * A stage taking place over a water area with spiked pillars that rise onto the stage, based on Super Mario 3D Land.
 * A stage based on Nintendogs, taking place in a giant room with a dog playing in the background.
 * A stage resembling World 1-1 from New Super Mario Bros. 2.
 * A stage resembling World 4-1 from Super Mario 3D Land.
 * A stage based on Kid Icarus: Uprising.
 * A stage based on Donkey Kong Country Returns 3D.

Wii U

 * A stage similar to Battlefield in Super Smash Bros. Brawl.
 * Skyloft, from The Legend of Zelda: Skyward Sword. (Much like the Delfino Plaza stage from the previous game, platforms rise every few minutes to change to a different location in Skyloft)
 * A wrestling arena-type stage.
 * A town, based on the Animal Crossing series.
 * Dr. Wily's fortress from the Mega Man series; The fortress itself is based on the design seen in Mega Man 2.
 * A stage based on Wii Fit.

Items

 * Capsule
 * Smash Ball
 * Wii Fit Soccer Ball