During the Nintendo Direct, Satoru Iwata confirmed that the Mewtwo DLC will be available for download on April 28.  Lucas was also confirmed as a returning character and will be available to download in June.  New Mii costumes are coming as well that will include: cat suits, monkey suits, Zelda suits, Xenoblade suits, Mega Man X, Proto Man, and more.  Nintendo will also continue releasing new amiibo figurines for all of the Super Smash Bros. characters including Mewtwo and Lucas.

Nintendo is also giving fans the ability to request characters through the “Super Smash Bros. Fighter Ballot” on the official Smash Bros. website.  This allows fans to directly (moves hands towards screen) submit their character requests to Nintendo.  To do so, just visit SmashBros.com.

Source: Nintendo Direct