Found some info here...
http://www.pcmag.com/article2/0,2817,2281491,00.asp
In part, it says (re SanDisk):
Product-wise, the company made no major announcements at CTIA, but company reps did confirm to us that the previously announced 12GB microSD size will not be released. Instead, this summer the company is going to "jump to the next obvious size," which is 16GB.
Apparently the 12 giggers previously 'available' are all only pre-orders?