If a recent video uploaded to YouTube is found to be legitimate then we have confirmation of several new characters coming to Super Smash 3DS via DLC.
A video titled Super Smash Bros DLC Demonstration LEAK has been uploaded to YouTube by a user claiming to have received an early DLC review code. In this short video he shows the character selection screen which highlights the inclusion of several new roster spots. Mewtwo, Wolf, and Waddle Dee can be seen in the video, albeit very blurry and seemingly out of format.
There is no confirmation regarding the validity of this video. We will update this post when more news becomes available.