Chances are IF it is; it is a selectable option. For any pre-release screens, it's probably turned off as to not show off any new unknown Pokemon.
However, as others before me have said it's probably not available. Why they use the storage they use now for DS games for now is beyond me? Why can't they move onto something like a bootable SD Card? It could make the game a LOT bigger, especially if it were like 8GB or 16GB. I think most games would even fit on a 1GB or 2GB SD Card. If I remember right, Emerald was 17,000 kb; and D/P were like 64,000 kb. So Platinum, was probably around 80,000 kb; and HG/SS was probably somewhere in the 100,000 kb - 150,000 kb. Now if I'm correct then the DS should play games on an SD card considering that 1 GB is 1048576 kb.