[Tuor Turambar,Cursed by the Valar]

Well, moria could not really be reinhabited if the dwarven population was declining enough to not populate the places already populated. What I mean is, if the overall dwarven pop. is falling, then it makes no sense to send dwarves away from the main center of pop. and settle somewhere else. Usually settlements build when there is extra pop. However, if Balin was willing to go to Moria near the end of the third age, when the dwarves were already in decline, then you cannot know if any other dwarves would have gone back to moria.