Some airlines manage this dynamically, to a greater or lesser extent, as part of normal yield management. So seats can come back in to the award inventory closer to departure time.
However, if you must travel on those dates, waiting is a very risky strategy. If you wait but award seats do not materialise, you could easily find yourself paying a much higher fare than you would have to pay now, because all the lower-priced revenue booking classes have also sold out in the meantime.