No, the 4S offered 16/32/64 just like the 4.
I don't see Apple eliminating the 16GB base model.
odd, when i bought my iPhone 4 the top of the line storage was 32GB...8-16-32 models
not that this is proof: http://en.wikipedia.org/wiki/Iphone_4
and looking at the bottom of the iPhone 4S page (maybe on teh iP4 page as well) they have a nice chart showing the storage of models and it is steadily increasing.