This same codename was leaked by DigiTimes as one of two iPad 3 prototypes being tested by the company.
Apple is currently giving two tablet PC projects codenamed J1 and J2 to its upstream partners for development. The sources revealed that the major differences of the new tablet PCs compared to the previous model are their size, specifications and technologies. Since the new tablet PCs have a higher resolution, Apple has demanded the design of the light source to be changed from a single LED light bar to two LED light bars on the left and right sides of the machine, but since the method of adopting two LED light bars has created difficulty in shrinking the machine's thickness, some vendors have come out with designs that only adopt one light bar, but are packing two LED chips into one package.
The discovery of the 'J2' codename in iOS 5 adds some weight to the information leaked by DigiTimes' sources. We'll keep you up to date with more information as it becomes available.