If all other factors are eliminated, size of aquarium, waste accumulation to a point of negative effects, and any other limitting factor then theroetically the population could grow unhindered to match the ever increasing amounts of ammonia. With any of the above factors in play, the population has to stop growing because it will reach the maximum amount that can fit in the container or the entire system will crash and all the bacteria will simply die.
The only thing that truely limits anything is resources, in this case food, heat, light and most important, space. Unlimited amounts of resources could mean unlimited amounts of bacteria but in our aquariums the space factor will always limit the population of bacteria.
I hope so anyway. 8O