Super Mario Maker
Let's face facts. When the NX appears, there's a good chance Nintendo could release updated ports of existing games on the new platform. It's very possible Super Mario Maker will be one of those games. Maybe it'd be a good time for local cooperative multiplayer? The New Super Mario Bros. Wii games had cooperative multiplayer. Maybe it'd be possible to allow couch co-op for levels that use that theme? It'd certainly give people an excuse not to go with the original Super Mario Bros. palette, with its many costumes.