Does the 4s get faster download "4g" speeds than the og ip4?
From what I have heard from different AT&T CS reps when I called them, as long as you stick to a smartphone with AT&T you keep unlimited until such time that AT&T discontinues it. I pre ordered iPhone 4S and kept unlimited data so I would contact them if you do not see that option but you should keep it.
If you are switching from another phone type to iPhone, you may have to call them first if you do not see the option for Unmlimited Data
i have iphone 4 , and have unlimited data on it .. and get no option to keep my unlimited plan