We're going to get at least two more Pokemon games on Switch. Some combination of Let's Go 2, Sinnoh remakes, and/or Generation 9 games from 2022 to 2024.
A new 2D Super Mario could do it if they break out of the "New" slump. NSMB Wii sold over 30 million copies on a platform where some people never bought anything after Wii Play.
A major new casual game like Brain Age, Wii Fit, or Nintendogs could possibly be released. Ring Fit might end up being a sleeper 10+ million seller, though I wouldn't count on it. Maybe a new Tomodachi?
Also, there could be some new peripheral or something that gets popular and includes a game that gets bundled into popularity. See Wii Play, Wii Sports Resort, and Duck Hunt.
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Overall, I think we're in for at least one upcoming 20+ million seller, either a 2D Super Mario or more likely Pokemon.
