I've heard of this to but going by the current price of the non retina pro (at least down here at the moment) I would expect the 13" Air to be a more tempting option.
I know!!! The Non Retina Pro is now $1549 even at JB Hifi!! Lol. People will still buy it because of the pro label, even though for some users the Air would be a better deal. The thing is thought that everything is more expensive. I don't know if that will translate into a complete drop in Retina Pro Sales and a pickup in Non Retina and Air sales, or just a pick up in Air sales...
The Non Retina Pro is massive with uni students who need lots of storage space, as well as PC to Mac switchers. I personally hope people keep buying them to get Apple to upgrade them, otherwise I don't know what I'll do with replacing my current Macbook when the time comes :'(