On my quest to be popular, and more so...getting comments, I created as realistic PS4 speculation w/o knowing anything to amuse anyone who wants to read this....
It's going to be based on the octal-stress technology, the successor of the Dual Stress technology based on PS3 and IBM's most powerful server IBM System p5 595. Seeing that technology will appear in 2 1/2 years in the future. 2 1/2 times 2 = 5 years justifying when PS4 may be released.
Although some people believe the PS4 will have download-only games onto a gigantic HDD like the Phantom console, I believe it will use a Quad-layer Blu-ray media, and a little 80 GB HDD. 512 MB GDDR7 on Geforce 11 is what I believe the vram will be based on . 512 MB XDR2 based on CPU clock speed. The controller will be the SixAxis 2 (/w all Wii remote's tilt and wave features!) The CPU most likely be a Cell at higher clock speed and quadruple the SPEs. SPEs are like cores except no brain..SPEs handle raw data which is controlled by a single PPE. PS4 will be $600 like PS3 at launch.
Playstation 4 supports Unreal Engine 4.0 thru Unreal Engine 4.5, Lithtech Triton, CryENGINE3, and many games will be developed on Unreal Engine 4.0 because that is one way to find a crowd who will spend that kind of cash on it when Gaming is even more mainstream than now.
PS2 emulation will be perfected in PS4, but you can't tell the benefits because the CPU costs a bit more at smaller silicon process.
PS4 will have a large amount of sequels to sequels on PS3 (Madden, DMC 7, Gran Turismo 7, Resident Evil 7, Final Fantasy 15, Wild Arms 8, Winning Eleven 15, NBA 2k?, Major League Baseball 2k?, Metal Gear ???, GTA6, GTA7, )
Only hardcore gamers will play PS4 because it's too high-tech for the mainstream gaming like what makes Wii popular..hopefully a Wii-mote SixAxis hybrid controller will help them.