I'm not so sure a real breakup would be the answer.
Let's say the PlayStation branch was broken off on its own. 1 or 2 generations of bad performance could kill Playstation forever. Wheras if it were kept in the main company it could be sustained during bad times only to surge back when times are good. Case in point PS3 vs PS4. PS3 could easily have gone the way of the Dreamcast. Instead Sony was able to keep in the game and thus PS3 ended up not being the complete disaster it should have been, because Sony was able to stick it out and pump more money into the console and keep the games flowing. PS3 could easily have been the end of Playstation, thus we would not have the PS4. That would have been a tragedy given how shitty the Wii U and XONE are right now.
A very long view needs to be kept in mind if a breakup is going to happen. What should be kept, what should be spun off. Can a robust company be maintained if too much is spun off? Or will there only be just a bunch of mediocre has beens left.
Although, its funny that the most profitable part of Sony is the finance division...











