I test drove a new F-250 and F-350 a couple of weeks ago. The F-350 ride was quite firm and no jostling. The F-250 jostled quite a bit more. When I hooked up my 5,000 lb dry weight trailer the F-350 dropped about an inch. When I hooked up my 2008 F-150 with no tow package it probably dropped about 4", but it sits on a OEM rake so still didn't look like the butt was dragging.
So I'm just guessing the new F-250 might drop 2-3".
BTW, the new Superduties are fantastic trucks! I'm in love with mine!