To answer the question OP asked: Nope, can't see them in store just yet. Will probably have to wait until each size is actually available before the stores start showing them.
I was at an Apple store yesterday and they still only had the previous gen iMac and Mac minis on display. I would imagine the new iMac will only be on display once Apple announces they have shipped. The model they showed at the even was probably a pre-production unit.