Nintendo's Shigeru Miyamoto has confirmed that Super Smash Bros. for Wii U will be launching at the end of this year.
A translation of his statement was posted on Twitter.
It's important to note that only the Wii U version of the game is mentioned. Perhaps Nintendo is looking to space out the release of the console and handheld versions. It would make sense to release the Wii U version first, especially if the company wants gamers to buy a Wii U just to play the game. Otherwise I bet a lot of 3DS owners will just spring for the handheld version.