I don't think he was referring to "middle class" in the same sense you are. You are using "middle class" to describe a certain standard of living. The author is saying that we will all achieve this standard of living and it will no longer be a status marker.

You can already see this occurring. Having a cell phone, for example, is not a status marker anymore - everyone who wants one has one. Status is now about having the most pictures/friends/farms on facebook.