The console market is too competive for a fourth major company to survive. Microsoft had to spend a lot of money to make the Xbox 360 a viable console for consumers and incentivise developers to cease their exclusivity with Sony. Apple don't have the experience, connections or funding to do that.
However, Sony should consult Apple when developing the PS4's OS and designing the GUI. Sony are one of the best hardware companies in the world (the PS3 is a testament to that), but their ability to make software is severely lacking. This was highlighted by their lack of ambition for the community aspect of gaming this generation. With the help of Apple or any other software giant, the next Playstation will undoubtedly have all areas covered.