You're not going to see 8GB of RAM in Sony and Microsoft's next consoles. At current densities that would be 16 x chips of DDR3 or a ridiculous 32 x chips of GDDR5. The motherboards would be bloomin huge and overly complex and the consoles will cost a small fortune. Not going to happen.
People's expectations of the PS4 and 720 are way too high, there are probably going to be a great deal of disappointed people once the specs are known.