Masahiro Sakurai tweeted that a trailer for a new Super Smash Bros. will be shown during Nintendo's E3 Nintendo Direct. During which Nintendo also sent confirmation to Official Nintendo Magazine that there will be two versions of the game, one for the Wii U and one for the 3DS.
This is big news, especially for me, since Super Smash Bros. Melee was the reason that I chose a GameCube over a PS2 back in the day and Super Smash Bros. Brawl being the main reason why I got a Wii. I spent over 800 hours in Melee and enjoyed Brawl quite a bit. I've been looking for a solid reason to even consider getting either a 3DS or a Wii U. So far, the games I want for those both platforms are Project x Zone for the 3DS and Bayonetta 2 for the Wii U. This new Super Smash Bros. might just seal the deal.
Source: [Operation Rainfall]
Update: You can find the trailer for the new Super Smash Bros. for both 3DS and Wii U here.