Sony made a mistake with RAD. Could have been a great VR studio and given Sony by far the best VR dev team: London studio, Asobi, PD, Insomniac, Firesprite and RAD.
Imo Sony's next partners for acquisition could be Bluepoint, Arrowhead, KJP (if Kojima wants to be acquired), From Software and maybe Media Vision if the rumours of them working on a PS JRPG are true and it turns out well.
I think it's difficult to portray the RAD situation as a mistake. Sony's relationship with them was never defined by their ability to make VR games, which is something RAD only pivoted to after their relationship with Sony. But I don't disagree that having another VR studio would've been good for them.
Bluepoint and Arrowhead seem viable, more so the former. But From Software is not happening unless Kadokawa want out of the gaming industry. I see no other reason why they would let go of an asset as important as FS.
I do think that Deviation and Haven studio are possible studios that Sony is eyeing. But I imagine that first depends entirely on how their debut games perform + the working relationship established making said games.