A franchise is 2 or more games. Astral Chain is a new IP that was half-owned by Nintendo and half by Platinum, I'm not sure who owns what now. Nintendo published it and owns the publishing rights. I have no idea exactly who funded what or if they work with them in the same manner as they do HAL or Intelligent Systems since they have a long storied relationship with those. Maybe they did, but I can't find any information on it.
I can provide the information on that.
At this point Platinum has a close relationship with Nintendo, similar to some other external companies we've named (just not as long). EPD - Production Group No. 1 is the group at Nintendo tasked with working with Platinum, HAL, Intelligent Systems, Game Freak and Syn Sophia (among others):
Hitoshi Yamagami (the Producer of EPD 1): He was a Producer for Wonderful 101, Bayonetta 2, Astral Chain, Kirby Star Allies and Fire Emblem: Three Houses
Kaori Ando (Project Lead at EPD 1): She was a Managing Director of Wonderful 101, a Co-Director of Astral Chain and a Director on Tokyo Mirage Sessions
Makoto Okazaki (Project Lead at EPD 1): He was a Co-Director of Astral Chain and a Director of Style Savy: Styling Star
we will see but I really doubt it. look at mario and it was its anniversary too, we only got all stars...
Mario's anniversary lasted the whole fiscal year (the celebrations were planned for April before the pandemic happened). So as well as all stars the anniversary included Paper Mario: Origami King, Mario 35, Mario Kart Live: Home Circuit and 3D World + Bowser Fury. I'm not saying Zelda will get that much but it wouldn't be at all surprising for Zelda to get a bunch of different games in the current fiscal year.