The speculation I've heard is that there will be a 7S and 7S+ basically the normal date, with some new high-end "iPhone pro" (the supposed OLED one) that may not be able to ship at the same time and may come out a month or two later.

NO ONE can manage the production of OLED panels on the scale Apple needs them. Even the largest OLED phones have sold millions at the most.

Apple sells a few hundred million iPhones each year. Just let that sink in for a while.

Unless someone invents a brand new way of constructing OLED panels or a time machine, the 7S/7S+ won't have it.

There are rumors of an iPhone Pro that would have edge-to-edge OLED and IR face unlock and world peace built in. It would also be priced so ridiculously high that Apple could keep up with the display production.