They are quiet because they are negotiating with Phil Spencer to become part of Microsoft studios.I do wonder what's going on at YS Net. It's been about five months since release, over a month since the final DLC...if IV hasn't been greenlit (and it sounds like it hasn't based on Cedric's Q&A) then most of the staff must've moved on to other things. I bet most of the people who worked at YS Net were contracted for SIII only, not to mention the whole coronavirus thing.
The only other scenarios I can think of that would've stopped the team from disbanding by now is they've got contract work (making other people's games doesn't seem very Yu Suzuki, but you never know), or they're working on an Xbox port/preparing Steam features.
Unless I'm mistaken, we haven't seen inside YS Net, or had any real interviews or word from YS -- even just talking about the reception of SIII -- since release really?
Of course, it is a joke, but hey sillier rumors have been around like the sega one.