From Bulbanews, your community Pokémon newspaper.
Every character on SSB 3DS/Wii U roster to eventually receive an amiibo figure
Mewtwo's official artwork in Super Smash Bros. for Nintendo 3DS/Wii U
In this morning's Super Smash Bros. for Nintendo 3DS/Wii U livestream, which discussed new content available to the games, it was revealed by series director Masahiro Sakurai that amiibo figures for two DLC characters, Mewtwo and Lucas, are in development. Sakurai also stated that all 51 characters in the game's roster will eventually receive a figure, including Roy and Ryu, the two DLC characters released today alongside Lucas.
Although it is now known that a Mewtwo figure will eventually be released, no release date was given, tentative or otherwise. The next wave of amiibo figures, set for a release date this September, will include R.O.B., Duck Hunt, Mr. Game & Watch, and Falco from the Star Fox series, as well as the Mii Brawler, Gunner, and Swordfighter.
Mewtwo is the only fighter from the Pokémon series in the current roster of Super Smash Bros. for Nintendo 3DS/Wii U which has not yet received an amiibo figure.