The Nexus 7 is a rebranded Asus device that was talked about last year. Then consider the Galaxy Tab, and the basic fundamental that Android has never dictated the sizes of devices.
Only Apple so tightly coupled their API with very precise, specific form factors and sizes. It is impossible to view Apple's move (especially after widely criticizing a 7" tablet -- recall the sandpapered fingers nonsense) as anything but a me too maneuver.