Sounds like heaven with cattails. You are right in thinking that as water freezes up, this may become a real duck magnet if it stays open when others are frozen. At the same time, it sounds like a great place to hunt any time. I think you should hunt it now and occasionally during the course of the season. While a person likes to give ducks a place to rest unmolested, we are hunters and spoiling a duck's day is what it is all about. Be careful not to over hunt the pond but not to hunt it at all seems like a waste. I been looking for that pond for years here in SD and if I found one just like it would hunt it discriminately all season. Visit it occasionally and secretly, but visit it with a few decoys and enjoy it.