PS4 should have.
HARDWARE:
CELL chip with 2x PPE, 16x SPE - 1 SPE reserved for redundancy, 2 SPE's reserved for the OS. --> thus leaving 2x PPE and 13x SPE's @ 5Ghz.
New graphics chip -- based off NiVida's GeForce 11 or 12 series.
1gb of RAM on CPU. 2gb of RAM for the video card.
12x or 16x blu-ray drive.
250gb HDD (if its cheap enough use a 120gb+ SSD)
FEATURE SET:
PS1 BC, PS2 BC, PS3 BC
Use XMB style interface
in-game XMB at launch.
Custom soundtracks in every game
Trophy support for all games
PSP/ PSP2 compatibility.
Cross game voice chat
HOME standard (provided its good)
Uses current PSN accounts.
Can access PSN - PS3 Store
PSN - PS4 store
Video store
Ability to take screen shots in all games.
Ability to view photo's in-game (not sideshow features though)
A good web browser...
In-game web browser access.
Finally -- good 1st party launch titles...







