There are signs of always-on display in upcoming iPhone

New iOS 16 beta version has hints of possibility for iPhone always-on display. New Lock Screen background has "sleep" mode which makes background darker and less colorful. While this still might be used for night time only, this might also be used to save OLED screen power for always-on display.

Reference: Latest iOS 16 Beta Further Suggests Always-On Display Coming to iPhone 14 Pro