Yeah, it will be interesting to see. Right now the Airs have much more availability in the pre-order stage than the Pros, and it could be because it's so new and different that people want to wait for reviews or until they can hold them in their own hands and try them, and maybe they fall in love with it at that point.I suppose that's what we're going to find out in the coming months as more people see the Air IRL in their friends' hands or in store.
My gut says a decent amount of 'every day' (read: not people who have even read an Apple forum, let alone participated on one) people will walk into a store, hold it and go "I can handle it only having one camera [insert other compromise here] - it's good enough for my needs because it's SO nice and the others feel like bricks".
So far Apple has had a lot of problems finding a solid fourth offering in their phone lineup. They went from Mini to Plus to Air and it will be interesting to see if positioning the Air as the most premium in design will give them a hit where the standard but different form factor phones didn't.