Nintendo is making the Switch but many are wondering how backward compatibly is going to work on the platform. The publisher is known for offering BC support for past systems with the Wii supporting GameCube games and Wii U supporting Wii games. Nintendo President Tatsumi Kimishima gave a comment addressing this concern stating that while BC isn’t on the table, support for Wii U/Wii controllers could happen in the future.
So while it is a shame we cannot play games like Mario 3D World on the Switch via BC support, at the very least we might be able to use the Wii U Pro Controller at some point in the future. You can find the official quote Tatsumi Kimishima provided at the above IGN video at the 1:22 Minute mark.