In a Q&A following the Nintendo Direct at E3 today, Nintendo confirmed that Super Smash Bros. Ultimate is an entirely new game built specifically for Nintendo Switch rather than a new version or port of Super Smash Bros. for Wii U.
Nintendo’s Bill Trinen and Nate Bihldorff also confirmed that in addition to internal Nintendo developers and director Masahiro Sakurai’s Sora Ltd., Bandai Namco is also once again participating in development as they did on the Wii U version.
Nintendo did not provide further comment when asked by IGN to break down the development responsibilities of each team, but did confirm that the teams are working closely together as well as with the rights holders for all third party characters.
Source: IGN.com Smash Bros. Ultimate Is a New Game, Bandai Namco Still Involved