We won't see representative numbers until around December.
The early adopters are more skewed towards buying the Air. But as time goes on, the less risk tolerant mainstream buyers will enter the fold. They're far less likely to choose the Air because of obvious reasons. We're already seeing this as all Air colors and storage configurations are now available for immediate shipping.
That could absolutely be the case, but I think you could also make an argument that early adopters are overwhelmingly overrepresented by tech enthusiasts who are more likely to choose the Pro phones, and that people who buy their phone at the carrier store will go in, pick up the device, and opt for it because it's (IMO) so much nicer in hand.
I know anecdotes are not data, but Ben Thompson of Stratechery fame shared on Dithering yesterday that he ordered a 17 Pro, was out and happened to go into an Apple Store, picked up the Air and almost immediately opted to return the Pro for the Air despite having previously saying on multiple occasions that he didn't know who it was for and that the he couldn't "tolerate the thought of running out of battery."
Will that be everyone? No. I personally think the Air will be the least-popular model, as much as I love mine. But as someone who has held all 4 phones (Air, 17, Pro, Pro Max) and spent significant time with two of them (Air and Pro) and is coming from a Pro Max, I could see an iPhone Air being more popular than many on here think.