Just a new form factor (thinner iMac) from getting rid of the optical drive is good enough to drive sales. Retina display can come later. They're certainly not going to put all their eggs in one basket.
Why do people want to dump the optical drive on an all in one to achieve thinness on a non portable desktop? Are you going to hang it on the wall. It already has a small footprint. To me, it's a step backwards. I'll need at least one optical drive and it may as well be in the desktop computer instead of eating space on the desktop.