HR 669 requires that petitioners pay to have animals evaluated to be added to the list. A 24 month scientific risk assessment as mandated by HR 669 can potentially run into the millions. I don't know of anyone (or even two, three, or 10) breeders in the business right now given the economic climate that could foot the bill for ball pythons to be considered.
As for other pets, I'm sure the situation is even worse.
-adam