Crappies are a very effectable species. Once they become overstocked in a pond, they are stunted and will not grow anymore. A farm pond that I used to fish literally had thousands of crappies in them. Over one summer, my father and I, and his best friend and his son caught 100 crappie in a single day, for 5 weeks straight. All of them were between 5-8" long. Not a single one of them ever reached 8 1/2" or bigger.
However, once we started pulling the smaller crappies out of there, we started noticing that they were getting larger. Where we were averaging 100 crappies that were between those lengths, we were averaging 25-30 crappies that were finally getting bigger than 9-10" and we were catching some that were 12-15" long.
With that being said, I have not fished that particular pond and I do not know the state of over-population that it has. The only way to truly find out is to catch as many crappie as you can. If you start seeing that they are all a certain length, and do not get any bigger, then that's the size that the majority will be. I am certain that there are bigger crappies in there, but as to being a trophy size crappie, I could not say for certain.
Another thing that determines the ultimate size of the fish in a body of water is the actual size of the body of water. If they have enough room to spread out and have adequate forage, they will become larger. If they are cramped, they will be stunted.