No, I don't recommend waiting for a better deal as one is unlikely to materialize. In general, buy tickets when you're ready as prices will only go up. DLR has recently been raising ticket prices annually in the Sept-Oct timeframe. I recommend buying now if you're comfortable with the price. I always buy from UC and find it to be one of the consistently best priced locations for park tickets. If you end up having to cancel your trip, you can get a partial refund from UC or apply the value of your ticket purchase towards future tickets with them (if going beyond the expiration date).
I've even bought 3-day tickets with UC in the past, then modified to 5-day tickets and they worked with me to make the change at no cost (other than paying the cost differential for the longer dated tickets).