I am not clairvoyant, but I bet that unless on Earth a new fashion emerges, they call it:
The earth.
That is what we call it down here, much as we call down "down" even though we now realise that the concept is relative, without any necessary connection to avian integument or the centre of the Earth.
After all, even an electrical earth has very little to do with the Earth nowadays, especially when we are dealing with the technical requirements of electronics. I often remember the expression on the face of a friend of mine, an advanced electronic engineer, when he found out that the "earths" in a new electronics lab had been connected to the building's piping for a good earth connection... I may not know much about electronics, but I can diagnose a volcano fairly well!
So if an earth isn't necessarily an earth on earth, why shouldn't it be an earth in heaven? (I mean a heaven in ... Well... you know what I mean!)
