Jul 21, 2018
Above is the what looks like will be the pricing matrix for 2018 iPhones vs 2017 iPhone lineup.
Also from an inside source / person in the know - code named AC - The "Fall" event will be Wed Sep 12th, Preorders starting 12:01 AM Sep 14th and Launch / delivery of new iPhones starting on Sep 21st.
I talk more about the new iPhones in Ep 467 of Today in iOS.