Problem still is that the GFlops mentioned in the source mentioning the HD 79xx would be more in line with a HD 78xx.
Most (on various other websites) assume that whoever wrote the article doesn't know much about hardware and it's simply a typo (HD 79xx is way overpowered for a gaming console and produces too much heat). PS4 would easily cost $600+ again if they use that piece of hardware.
But even a HD 78xx would be great hardware for next gen.