It looks like Mario + Rabbids: Kingdom Battle downloadable content for added story missions could be coming to the Nintendo Switch in June. The news was spotted on the Japanese eShop where the game has yet to launch. Ubisoft and Nintendo have yet to confirm when we are getting the additional story DLC other than this year.
Not a Nindie, but I think I stumbled upon the DLC date for the story expansion (atleast in JP) for #MarioRabbids... on the Japanese eshop listing for the expansion pass it lists this. @grantkirkhope @DavideSoliani #NintendoSwitch pic.twitter.com/RpDHUgGz8i— Switch Nindies (@SwitchIndie) January 3, 2018