I'd say any reuse of material due to it being a direct sequel would be counterbalanced by the added workload of HD tier vs Wii-tier development.
I simply can't see BOTW2 realistically arriving this year, not with the team's track record. I'd love to be wrong but I'm certain I won't be.
That development group has made:
New Super Mario Bros. U
Mario Kart 8
Super Mario Maker
The Legend of Zelda: Twilight Princess HD
The Legend of Zelda: The Wind Waker HD
Wii Fit U
The Legend of Zelda: Breath of the Wild
Mario Kart 8 Deluxe
Super Mario Odyssey
New Super Mario Bros. U Deluxe
Super Mario Maker 2
Animal Crossing: New Horizons
I hardly think they are new to HD assets.
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