My guess is full fledged remake ala FF7 Remake. 

They already have an engine seemingly for it (see Wii U Zelda demo) anyway. 

I think they want to tie in to the Zelda movie next year and this will sell through that movie release window but to bring that game to a new generation of consumers a 3DS port probably doesn't cut it lol. 

We'll see though, who knows. 

Ocarina Remake would be day 1, assuming it isn't a remaster. I already can play it upscaled, with overhauled controls and texture packs.

Looking back at that Wii U Zelda tech demo ... I kind of doubt this was ever running off actual Wii U hardware. It looks better than BOTW/TOTK (aesthetic debates put aside). 

But Switch 2 could really make an engine like this cook and enhance it significantly. A OoT Remake that looks like this but better would be outstanding. 

They could really enhance the story too ... OoT actually has a pretty cool story, but the derpy N64-era visuals really could not convey it that well and lacked punch.

All of this along with the evergreen effect of Pokopia leading the charge could make this a solid year for Switch 2 even without the new Mario. Let's just hope for no price increases.

It depends on how big of a scope that Zelda remake is. If we're talking like FF7 Remake type of deal and care put into it, or even if it's running on that Wii U demo engine (enhanced) ... that would be a big, big deal. 

Duskbloods could be a big deal too.