Not so sure about this. We still mostly have laptops with shit 1366x768 monitors despite "retina" or at least "full hd" screens being around for quite a while...
Given that Dell's 5k 27" screen is priced similarly to these iMacs, I think the economies of scale could help push some prices down.
Walk through any best buy and that res will far and away be most common.
I for one welcome our new high-DPI overlords.