No SD slot would be the killer for me (well that and being forced to do things the apple way thru itunes). Especially when one of the main selling points is social viewing of photos on a bigger screen than a camera.
TBH, plug in messy dongles and cables isn’t really the Apple way. Mind you 90% of ipads never leave the home anyway, so using an ipad away from home to view pics is probably quite rare.
I’ll stick with my tablet with flip out (proper) keyboard that cost a fraction of the price and has 3x the number of USB ports as the Macbook Air, and runs apps for free, with a choice of “stores”…