If Apple does go quad core CPU + quad core GPU, presumably they are going to have an inventory of partially defective chips. The iPad and iPhone are going to need full chips for competitiveness, but the next iPod Touch could presumably make do with spec reduced, fused off parts. A quad core Apple A6 disabled to dual core CPU and dual core GPU would look much like an Apple A5, but presumably would have battery life benefits from being 32nm, additional clock speed room, and make use of chips that would otherwise be thrown away. I don't suppose a triple core CPU configuration is easy to support? I'm guessing PowerVR doesn't support a MP3 configuration?
Making use of defective parts gives Apple more configuration flexibility while maintaining the 1 SoC/year development cycle. The iPod Touch is probably the lower volume platform compared to the iPad and iPhone which should reduce concerns that they'll need to disable many good chips just to supply the Touch as yields improve.