optimistically, six seasons. each season, a fallen angel from div. II arrives. from below, top notch (for the most part) div. IV teams. and these div. III coaches know what they are doing (scrimmages, playing time, handling enthusiasm, training, having money available for million dollar acquisitions).
i think it more likely to move back down to div. IV then onto div. II.
in a few more seasons, div. IV will start taking on these characteristics.