I was going to say we'd be very limited in characters that could be revealed, but looking at the list of potential newcomers and the list of upcoming games (or games eligible for (additional) DLC), this might actually work. We wouldn't get any retro characters, but to be fair - those tend not to get announced early on.
For those wondering, these are some of the games that could be addressed in Nintendo Directs:
- Mario Tennis Aces
- Mario Odyssey (DLC)
- Captain Toad Treasure Tracker
- Luigi's Mansion
- Donkey Kong Tropical Freeze
- WarioWare Gold
- Hyrule Warriors Definitive Edition
- Kirby Star Allies (DLC)
- Pokémon Switch
- Xenoblade Chronicles 2 (DLC)
- Metroid Prime 4
- Fire Emblem Warriors (DLC)
- Nintendo Labo
- Dillon's Dead-Heat Breakers
- Yoshi Switch
- Mario & Luigi BIS+BJJ
- ARMS DLC might be done, but there's that tourney coming up
- A truck full of indies