I’d imagine both the Air and Pro lines would get updated every year. Both using the same generation of chip design. The difference between the air and pro would be: higher core counts, better multi-thread sustained performance, better GPU, XDR screens, more ports, more ram capacity, more storage capacity, more external displays.
If they were to put an older chip design in a Mac, I would prefer that to be called maybe a MacBook SE or something. So it’s the cheapest options using and older design. I could see the current MacBook Air design sort of filling that spot in a few years after they update the air to a newer design. Maybe they could sell it for $799 or something. Who knows.
IMO the biggest issue right now is how they have a 2-port and a 4-port version of the 13” MBP. It’s confusing to some people because the 2-port version is also less powerful (I know right now it’s not because of M1 but traditionally it’s the lesser of the 13” models). It’s not clear by the name. If they just got rid of that, and had two air’s instead I feel it would eliminate the confusion.