I think they're looking at how the market behaves, they have various scenarios:
1. people like the hybrid console and 3ds sales continue, fail on mobile apps market: they'll keep working divided projects for portable devices and "main" console devices. And announce a 3DS succesor.
2. people like the hybrid console, people lose interest in 3DS, and top grossings on their mobile apps: they they'll make those kind of "portable" Zeldas for the Switch but with alternate stories (like putting a Tri Force Heroes in between a "big" Zelda release). and also putting small game apps like Fire Emblem mobile.
3. people dont like the hybrid console, and 3ds sales continue: unlikely
4. people dont like the hybrid console, 3ds sales fail but top grossings in mobile apps: Nintendo stops their hardware attempts and focus on software for other hardware like SEGA did.
So I do hope and feel they'll continue doing this kind of Zeldas, and not only for the market behaviour as the points above, but also because they have other dev teams, that can deliver smaller Zelda projects in between.