DJI have just put a Phantom 4 Battery Charging Hub on their web store. Although looking different to the one for the Phantom 3, it charges in sequence of battery with lowest charge first ( so one battery at a time ) but this only does three batteries and not 4 that the Phantom 3 version did.
One big difference between this and the P3 one is the DJI have added a “Storage” feature that they say keeps the battery at 50%. It does not mention if it only charges to 50% or that it will discharge a battery to 50% also.. Waiting for mine to be sent to me to have a play..