8-16gb memory, the 256mb memory in the PS3 was laughable in 2006 when it was released especially considering the OS takes 46Mb of memory, you couldnt give away a pc with 256mb of memory and 256mb of vram today.

minimum 3gb Vram for PS4 the (256mb was very average in 2006) The PS3 should be at least 1080p 3D HDMI all the way, no composite possibly component but no bother if ads cost

4-8 cores 16 virtual threads at least 4ghz in speed at least
or a 16 core cell running at 3.8ghz

well ventilated and quiet and never overheats no ylod rlod blod bullshit this generation of consoles have suffered from ad infinitum
hence 32nm technology at least possibly even 22nm to really make them quite and cool

solid state boot drive 64gb in size partioned into 2 partiition 32gb for PS OS and 32gb for fast game sroage cach, with additional green quiet 1tb/2Tb 3.5″drive storage, fully installable games no enforced disc access.

blu ray is still a standard so include, ejects disk on game launch to lower noise levels in game

external power supply to aid cooling efficiency

tower design air in at the bottom/front air out at the top/back 120mm quiet dual fans filtered properly with foam and insulated to reduce noise

Bluetooth 4.0 surround sound audio with game and chat audio mix capability for bluetooth headsets and optical surround sound out amps

wireless N

gigabit ethernet

voice input from dual beam noise cancelling mics, camera included for tv top with the console ? possibly

somehow a touch keyboard built into PS controller, use vita perhaps as controller for PS4 as since the smartphone tablet era inputing text on a standard PS3 contoller is the Definition of Archaic

next gen quality motion control controller no stupid ice cream cone light on top ? distracting and stupid looking