Here are some things we might see in 2020.
1) The usual suspects - games that regularly come out on handheld or home consoles.
Wario game (either platformer or smooth moves)
2) Revive old franchises
Lots of others. Too many to count.
3) Ports & Remakes
There are still a few Wii U games left to port. On top of that we got Link's Awakening this year and Xenoblade Chronicles is on the way. Nintendo will likely have at least one other port in 2020 either from the Wii U or an older console.
4) 3rd Party games using Nintendo IP
The Switch already has Mario + Rabbids, Hyrule Warriors, Fire Emblem Warriors, Starlink (w/ Starfox content), and Cadence of Hyrule. They are showing that they are actively trying to get 3rd parties to make exclusives for Switch using Nintendo IP. I doubt this is going to stop.
Pokemon, Mario Party and Kirby sequels are definitely going to come eventually (though not necessarily in 2020), and we already know about BotW. Mario Odyssey, Mario Kart, and Splatoon are all games that may or may not get another game on the Switch. Also, while technically a Square Enix game, I know the Octopath Traveler team is working on a sequel or some game like it.
6) New IP
So far we've gotten ARMS, Snipperclips, 1-2 Switch, LABO, and Ring Fit Adventure. (I may have forgotten a game.) Nintendo is putting out at least one new IP a year. I would not be surprised to see this rate increase either considering how successful the Switch is. Nintendo can afford to be more experimental at this point.
Wario ware- yes please! Tomodachi.- If done right and online multi- Yes please! Mario Sports- yes please! Wii sports (or similar)- Yes, pretty please!
Advance wars- yes please! Golden Sun- yes I would like to try a modern take on it out. Excite truck- Yes please with bells on it!
Also, on your revived IP's list i'd like to add a brand new Startropics. That i'd love to see!
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In my opinion the N64 was not just the best console of the 5th gen but, to this day the best console ever created!