We’ve been waiting for this since the game launched and it looks like two new pieces of Super Mario Odyssey DLC will be announced at tomorrow’s Nintendo Direct.
According to @Vandal_leaks (who was the first person to correctly predict tomorrow’s Direct), Nintendo will tomorrow announce two premium pieces of DLC (likely to be paid), with the first releasing next month. The best piece of news is the fact that it will be a Luigi’s Mansion Kingdom with 43 new moons.
Luigi’s Mansion is one of my favourite games of all-time and I’m definitely not alone in this sentiment, so I’m all for it!
New Nintendo Direct on 3.8.2018 
New premium DLC for Super Mario Odyssey and Pokken Tournament. Mario will get 2 DLC sets in the following months. The first on april 25th includes a brand new Luigi's Mansion based Kindom with new 43 stars for players to get.