Bowser's Fury Overview Trailer gives us more specific details

Nintendo has finally lifted the lid off Super Mario 3D World + Bowser's Fury in a seven minute video as well as on the official website overnight.

The first part of the trailer focuses on 3D World.

As for Bowser's Fury, we learn that it's a cat-tastic new adventure in which Mario travels to feline-inspired Lake Lapcat as he takes on the nefarious Fury Bowser. Scanning the new Mario will turn a player's character into White Cat Mario. The biggest inclusion is online play, which was not a feature on the Wii U version. There's also a new "Snapshot" photo mode that will allow you to snap pictures at any moment, add filters, and even place stickers that you collect onto your photos. Bowser's Fury does allow co-op play as well, but it's limited to local play only. Bowser Jr. can either be controlled by AI in single-player mode or by a second player during the game.

God Slayer Bowser is the name given to the large, "out of control" Bowser as seen in the Bowser's Fury trailer.

All-new Cat Mario and Cat Peach #amiibo figures will also be releasing on 2/12, both bringing in-game enhancements to #SuperMario3DWorld + #BowsersFury!

That's changed in this new release, as Nintendo has confirmed that there will be online multiplayer for Super Mario 3D World portion of the game.

We now know that Bowser's Fury is considered to be completely separate to Super Mario 3D World.

Join Mario, Luigi, Princess Peach and Toad on a quest to save the Sprixie Kingdom in Super Mario 3D World + Bowser's Fury, pouncing onto Nintendo Switch!