I doubt Sony has the Adrian Newey of chip design among them to upgrad the HD 7660D to something lasting them another 5-7 years.
I don't think more powerful APUs are about design breakthroughs. It's about target market. APUs aren't 'weak' in the desktop space because of technical constraints but because of the market they're targeting.
If a client comes along and wants a larger, more expensive APU, AMD won't need some godlike design power to make it happen. They're just dealing with different budget and die-size constraints than they deal with in the desktop APU space.