The iPad4,1 and the iPad4,2 are the iPad Air Wi-Fi and iPad Air Cellular models, respectively. The iPad4,4 and iPad4,5 are the iPad mini 2 Wi-Fi and iPad mini 2 Cellular models, respectively.
Thus its likely that the iPad4,3 and iPad4,6 are new models of the iPad Air and iPad mini 2. Perhaps a new version for China?
The firmware for the new iPads can be downloaded from here or below:
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