Your lack of knowledge is showing. How does Intel get 40/80GB for its SSDs?
The controller uses 5, 10 (and 20 in the future) NAND flash memory chips at a time.
64GBit (8GB) x 5 = 40GB
64GBit (8GB) x 10 = 80GB
128GBit (16GB) x 10 = 160GB
Thats how the X25-V/X25-M get their storage.
Many SSDs have wear leveling algorithm that reserves some of the NANDs that's not usable directly for the users.
This is what's the table look like for Sandforce controller based enterprise SSDs using 20% reserved provisioning plus 7% for GB>GiB.
Code:
Advertised, Total Flash, Useable Flash (GiB)
50GB, 64GB, 46.6GB
100GB, 128GB, 93.1GB
200GB, 256GB, 186.3GB
400GB, 512GB, 372.5GB
Customer SSD based is 13%,
Code:
60GB,64GB,55.9GB
120GB,128GB,111.8GB
240GB,256GB,223.5GB
480GB,512GB,447.0GB
Intel has some of flash reserved as well, around ~7%.
Anyway, I don't think Apple will discontinue 16GB. They'll have 16/32/64GB models. They discontinued the 3G 8GB, which could leave 3GS 16GB as the entry model.