Apple shipped the devices with the N capable hardware installed, and then tried to charge five bucks to enable the higher speeds after specification was officially ratified. Not surprisingly, there was serious backlash and the firmware update was made free after about a month. This is different. 4.2 requires newer hardware not present in these products previously. You could enable certain aspects of the 4.2 spec with a firmware update, but it would never be fully compatible.
10/9/15 at 9:52pm