Engines are scalable. New engines are not required like they used to be.

I am very skeptical that Nintendo is going head first into a series of remakes, given that hasn't been their style. They tend to remaster with a HD coat of paint. But hopefully I am wrong. Nintendo remaking their classic games would be a literal dream come true for me.

Engine get updated with new features - TotK iteration of it is already much improved upon BotW. There's no reason for them to build new engine, when they already have one that fits the bill. For whatever art style they choose (probably stylized realism, since that's what fits OoT the most), if its missing some features they need for that, they can upgrade it, not build from scratch.

OoT 3D already is a complete graphics overhaul for OoT, it's completely redone already:

That's why I doubt they'll remaster the same freaking game for the second time with no major changes. That won't sell systems either, just for the record OoT 3D didn't do much for 3DS sales and that was already a total upgrade/change in virtually every graphics category (textures, poly models, frame rate). You're going to have to add a fair bit of new content, some new story elements probably (dramatically more advanced cut scenes), and bring the graphics fidelity up to FF7 Remake tier level IMO if you want to actually move Switch 2 systems. 

I just realized more time has passed between OoT 3D and now than the original and OoT 3D.

The line between a new engine and just a big overhaul of an existing one can be kinda blurry; I remember one of the devs on the Call of Duty series stating once that buried deep in even the codebase is still code for damaging ground left over from the Quake days, even though the engine has been changed so much since then it's considered a different one.

I believe Retro is still using their RUDE engine dating back to Metroid Prime 1, just massively updated.

Making a new engine entirely from scratch is such a huge amount of work that most companies don't bother any more and just update the one they have.

OoT via emulation and upscalers actually looks pretty good.

UE4, damn good engine that is still used today, was released in 2014...  so correct.  Building an engine from scratch isn't needed and would be a giant waste.

Heck Rebirth uses UE4.  People suggesting a new game engine simply don't know their tech,  

It's also worth noting that using the same engines doesn't mean the games will look the same; these games all use UE4 but look very different:

Absolutely.  Games engines are versatile and scalable.  It isn't 1990 where new hardware meant new game engine.  Nor does playing the same games mean same hardware tier.  A lot has changed since the 90s.

It is also note worthy how long a good engine takes to develop.  UE4 took 11 years to develop.  UE5 is still, imo, a mess.  

Yeah like you don't need to use the 2011 Wii U demo tech to make a more realistic looking Ocarina remake, nor would using the BOTW/TOTK engine mean it would look like those games.

If it's made in-house by Nintendo I can see them using an enhanced version of the BOTW engine with next gen tech built into it, while if they've gotten an external partner on board for it, it'll probably be Unreal.