Nintendo is reactive. It really depends on how successful the Switch continues to be in 2021. If the Switch is still selling like hotcakes to the point where Nintendo is having trouble maintaining supply, then why on earth would they want to tap the well and increase demand more by delivering more AAA titles hastily? That said, if the PS5 comes on to the scene and starts decimating the Switch's sales, Nintendo will react by teasing and pushing out a lot of what is in their pipeline. What we see come from Nintendo in 2021 will depend heavily on how much the Switch's sales start to diminish in 2021.
If the Switch drops like a rock next year (which I highly doubt, but let's just say hypothetically) then I think BotW2 could be expedited along with possibly a few new IP's, remakes and probably a pro model of the Switch that has upgraded graphics using Nvidia's AI upscaling or something. Nintendo would probably ensure that BotW made heavy use of the new upgraded graphics and that it is a premiere title of sorts for the new release to encourage people to upgrade from their current Switch models. There would also be a ton of hype around the new Zelda.
But even if the Switch drops like a rock next year, it will take a lot before we see the level of innovation that came from Nintendo in the latter part of the Wii U era and start of the Switch era (the genre re-defining megatons like BotW, Splatoon, Mario Maker, Mario Galaxy, etc...). At this point, the Switch will ride on momentum alone probably until it hits 110-120 million at the absolute minimum regardless of what Nintendo does. This is unfortunate for gamers in some ways, though, since Nintendo only performs at the top of their game when they are absolutely desperate. When Nintendo is successful like they are right now, they basically go into sleep mode until their next platform bombs. I wouldn't expect anything but lazy remakes from Nintendo for as long as the Switch remains as successful as it currently is.