The next Mystery Dungeon is in the works and is slated for a February 2019 release
They're called Pokémon Super Mystery Dungeon Red Rescue Team (3DS) and Pokémon Super Mystery Dungeon Blue Rescue Team (Switch)
Starters are Bulbasaur, Charmander, Squirtle, Pikachu, Vulpix (Red) Meowth (Blue), Psyduck, Machop, Cubone, Eevee, Rowlet, Litten, Popplio, Rockruff, Alolan Vulpix (Blue), Alolan Meowth (Red) and Stufful
It shares many elements from the first Mystery Dungeon but they are not remakes nor sequels
You can pick 2 partners now, but same rules apply as the previous Mystery Dungeon
Ultra Wormholes and Mewtwo play a massive role in the story
Story stays the same in both versions
Version exclusive Pokémon
You can't trade Pokémon but there will be a special friend area if you've interacted with the 3DS version
Pre-orders will allow you to have Riolu as a partner
Z-Moves are in the game but only against boss fights
Rotomdex is in the game
You can costumize your Pokémon in-game
It will power their stats or combine moves
One of them is the Link Hat