I don't think ninentado would even be interested in playstation. They are more of a legacy company and will keep on the lower end of the consoles and keep the crowd that buys Mario/Zelda/Pokemon. It seems since the GameCube they are mainly going to stay on the course they are planning.
And a merger of any of the 3 main console makers I don't think would ever get approval from the different governments around the world. No matter if ninentado/playstation, xbox/ninentado or xbox/Playstation the new group would have a huge advantage on the other one. And if Playstation would be sold, my best guess that the buyer would be someone like Amazon.
And for the earlier comment about Microsoft ruining halo and rare. Micosoft didn't do either of those. Bungie wanted to move on from halo for new projects and microsoft let them leave to make destiny. (And bungie already had the idea for destiny since atleast halo:ODST. And for rare, yes they are not taking games like they used too, but several of the staff that where there before the buyout have said that rare would have been bankrupt and most likely been gone.
http://www.gamnesia.com/news/rare-employee-believes-they-would-have-gone-bankrupt-if-not-for-microsoft







