I have a suspicion that there might not even be a Playstation 4...
Well, as in a physical box anyway. I reckon all games will be held on servers and content downloaded as and when. TVs will have extra controllers like gamepads and inside the TV will be a 'PC' which is what the PS3 is anyway.
You will simply switch over to the right channel and play any game you wish. No need for a physical console. TVs could all have a HD-DVD/DVD/BLU_RAY slot on the side for those that wish to play/watch old stuff.
SONY could even build a PS3 into their TVs....
Other TV manufacturers would simply have a PC built in and you could download whatever the latest Playstation software is. This means you could also download the latest games from Microsoft, Nintendo, ABC, FOX TV, Universal, whatever. It could open up the while market.
Basically, your TV WILL be a PC, your PC will be a TV and it will all reside in your living room.
That is, in fact, SONY's intention with the PS3, to make it a whole media center inside your living room.
Think outside the box... there is no box!