I think Sony should ditch PS4, and aim for something bigger, more flexible, resulting in the long term 10yr+ lifecycle they desire:
Playstation Vaio
Sony obviously has relied on certain tech to have an advantage over its main competition, but in this gen. blu ray was not enough. HTPC is the undeniable future for console gaming. Consoles have to put on as many hats as possible to avoid becoming "niche" again. We see the direction its going with all the video provider content on PS360, and now Wii U's Nintendo TVii. I can see a Vita-esque Vaio controller w/a small screen (keyboard essential) and trackball replacing the right analog stick. With Vaio entertainment you have it all, and can justify a $500 purchase. If they really want flexibility Sony can offer different entry levels divided by graphics card power, (might i add must be designed in a way where its easily upgradable for the everyday user). Yes not every one likes PCs, but everyone NEEDS a PC.
Essay Pro