You are up against DL's IM/RM software which says you are wrong. DL believes that it will sell the seats at M or better and can always open up lower buckets if it can't. But, if it sells the seats cheap now and later there is demand, it has left money on the table.

You can certainly wait, but DL's data presumably suggests that it will sell and that the price of available seats will go up, not down.