If one area is continuously plucked it's unlikely to grow back. We had this one year with one of our large, soft-feathered cockerels, which plucked his wives rear ends, presumably to make mating easier. It worked and the eggs had an excellent fertility rate, but the feathers never grew back (intelligent cockerel - scary thought, eh). Generally speaking, if the moult takes a long time the feathers will grow back over an equally long period and in the same order.