Even the iPad 3 is already available in the market with 4G support, Apple is still looking for new software engineers specializing in 4G LTE network. It should not something big to do with the iPad 3 and with this new job on Apple, everyone is turning their attention to the next iPhone which is currently known as iPhone 5.
Of course it should be time for Apple to develop the next iPhone with 4G LTE support or the company will lose some market share for those who want to enjoy the super fast speed internet.
So far as known, Apple might be interested in VoIP. The new software engineers are supposed to develop IMS VoIP which will allow users to make call between iOS device for free by just connecting to internet. Currently Apple already has iMessage which offers free SMS already. One more big improvement if this information is true.
If you are interested in the position, you can visit this page for more information.