I expect the air to completely replace the standard iPhone by the end of the decade.
It only seems logical, the standard iPhone is rocking the exact same design as last year, and is rumor to be completely skipped next fall.
They are already showing signs that the standard iPhone is becoming a “legacy” product and will likely either combined with the air or combined with the E.
Once the Air gets dual cameras in a stereo speaker, which it is very likely to get, there will literally be no benefit of the standard iPhone.
It’s exactly what they did with the MacBook Air, it started out as a weird premium option between the regular MacBook and the MacBook Pro, before it just *became* the standard.