This has been debated endlessly. The three simple reasons for a crop Z900 mirrorless camera are cost savings, weight savings and size savings.I guess I need some enlightenment. Why does Nikon need a mirrorless D500 replacement? The D850 in crop mode shoots just as well as the D500. Doesn’t that hold true for the Z9 as well? Now don’t get me wrong, I love shooting my D500 and I would probably buy a mirrorless D500 (Z?) once that arrives but I have always wondered why a complete line of new lenses had to be developed simply because Nikon developed cameras with crop sensors. And now they are developing a Z line of crop sensor lenses all over again.