This is just an example. 2021: a spin off with multiplayer feature like Tri Force Heroes. Let Go isn't just a remaster, it's a full remake. 2022: mainline game only if they reuse the same engine, if they built a new engine then not sure it will take only 4 years.
Sorry, i meant remake, not remaster. I keep using remaster as an equal to remake.
Yes, a mainline game by 2022 will most likely use the same engine.
But, it's not impossible for them to do something new. BoTW took so much time because of the transition to HD development (NMSBU took 3 years to develop!).