Or maybe, just maybe... there's nothing going on?
My read on the whole take is Sony seems willing to bet hard on Astrobot as a real competitor to Mario on Sony platforms, so they're boosting the talent on Team Asobi.
To do so, they're sending the Japan Studio talent towards Team Asobi, but of course those not interested in working on Astrobot are looking elsewhere.
It's not like Japan Studio has been spearheading any games anyway. They've been mostly assisting in remasters and remakes, but not even as project heads.
Team Ico pretty much disbanded to become GenDesign and those are the heads for the Last Guardian and its prequels' remasters. Bloodborne is a From Software game, and Demon's Souls is mostly a Bluepoint game.
Most of the people who worked in the Gravity Rush series had already followed the same path as GenDesign and formed the Bokeh Studio recently.
Some people are trying too hard to make this into the sudden destruction of a studio (akin to EA blowing up Maxis after the Simcity failure), but it just seems like the organic evolution of resource distribution.
The only franchise apparently being orphaned is.. well, Knack.
I tried to like Knack. And Knack 2. But I couldn't..
That's a Team Ico title who's talent has been independent since 2011 when Ueda formed his own GenDesign studio. It's not a title headed by Japan Studio.The Last fucking Guardian.