Why make too many of the 16gb models widely available when Apple makes pure profit for every capacity above 16gb.
I.e. if you buy the 128gb model, you are buying a $499 iPad Air and giving Apple $300 pure profit, period.
I am sure the 16gb will NOT be in plentiful supply at launch, but their will be gobs of 128gb model's available enticing you to spend $300 more. Apple will boast "unprecedented" demand limits supply, but nobody in their right mind wants to spend $100s more for a little extra flash memory you could buy at Costco for $9.99.
Apple's pricing structure on iPad (and all their products in general) is criminal, I don't know why there isn't a class action lawsuit against them. I'll be waiting for the new Nexus 10.