Superchunk I'm not sure if your OP has it somewhere but their is a big possibility the PS4 will not have a discreet gpu at all.
Given the latest rumour of the use of jaguar cores in the APU theres a big chance that they wont need to have a discreet gpu as they will effectively be able to fit a better gpu in the APU if that makes sense :)
All in all i think given the latest rumours there will be a significant bump in visuals next gen..and this should be accredited to AMD for creating low power solutions with high power performance. Really amazing stuff happening there IMO.