I think we'll see an imac before that. From my experience, earning calls doesn't really tie up to product releases. and iMac doesnt really need an introduction.
I expect early october at the latest. But, it could be earlier. Even 12th september is possible. Since Apple asked stores to remove mac mini and mac pro to get more space for pads it could be possible the wanted to leave the imac there since it will get an update at that time - because there's really no reason to display the current imac any more than the mini - its as old and take more space

. Fits with the fact that all stores seem to get out of stocks now.