if 16gb version sells like hotcakes across carriers then 32gb will likely be pushed back and/or have low availability. and it looks like the 16gb is selling very well so far with all the pre-orders being sold out or potentially being delayed "due to high demand".
the large majority of consumers can make due with "only" with the 16gb (9gb
) version because most don't use apps that require lots of data storage and the sd card takes care of the media piece. the carriers know this and they also know they can keep the price and their subsidies much lower with this version. margin and contracts are key.