According to a report, Samsung has started manufacturing LTPO and 120 Hz displays, presumably for the iPhone 13 Pro series. The pair are expected to arrive in September alongside the iPhone 13 and iPhone 13 mini. All iPhone 13 models are believed to have OLED displays.
https://www.notebookcheck.net/LG-and-Samsung-tipped-to-supply-Apple-with-OLED-displays-for-iPhone-13-series-120-Hz-and-LTPO-panels-already-in-production.541846.0.html