I don't see Apple moving in that direction. Especially after the lackluster sales of the iPhone mini and the iPhone Air compared to the Pro and Pro Max line.
Their core audience for the most part isn't particularly interested in getting a cheaper and/or features limited version of their baseline devices.
Maybe they could just drop the "Air" moniker from the current lineup, It's not like there's that much difference, cooling aside, from the Macbook Pro line.