With switch they finally have hardware that can push a realistic style well, and they decided to do an anime style, it will be interesting to see what they do after xb2 because they've only been able to push 1 title a console generation for Nintendo, but this game is coming so early and the switch is so easy to develop for, I think they will get a second and even 3rd title out on switch.
Not completely correct on the past. I mean, that's kinda correct for Takahashi as a director, but that also applies to him before joining Nintendo although his role in Xenosaga III was important.
As far as Monolith goes, due to their peculiar structure they've usually been able to output 4-5 "full" games per gen, more if they collaborate with others.
Currently it's not clear how deep their role is with the new Zelda, but since they went as far as putting it in their homepage beside XB2 I believe a good amount of personnel was "lent" to the Zelda team and I'd consider it reasoning about the future.
Anyway, I'm not sure how heavy is the development of XB2, the trailer totally gave me an idea of a smaller project than X and even XB were, one which can surely leave room for another important project to be in development in parallel (hopefully X-2).
It remains to see if team #2 has some involvement in this or they're another variable to be considered: although the two PxZ games weren't comparable to the Xeno games, they have proven to be able to ouput good/great secondary projects (without Takahashi) too, like Disaster or BK (and unlike Soma Bringer). The development context and experience from X should give a nice boost too as you say.
tl;dr: I absolutely see Monolith realeasing two more games other than Zelda and XB2 by 2020, and three could easily happen since they always have with normal platforms (bad Wii U, bad).