Considering its size I'd also have to say Japan studios, but hey maybe they can remedy this in this generation, the ex-SSM that is the head of the studio has been doing good work I've heard.
If that JRPG rumor is true (well actually I've heard about 2 JRPGs) and that game turns out to be great and a success as well and if they finally manage to get TLG out the door, I'd say they are well on the way of turning things around. Just imagine that JRPG spawning a successful franchise, when was the last time something like that came from Japan Studios?
Edit: Also to be speculating a little Japan Studios does have the Silent Hill creator working for them and P.T. was exclusive to the PS4, which has started some discussions about Silent Hills maybe being PS4 exclusive as well, maybe Silent Hills will be a collaboration between Konami and Japan studios and will have Toyama working on it.
Well anyway, what I'm saying is that Japan Studios have been pretty poor in the last couple years but they still have potential and are definitely very important, Sony needs a big japanese studio.