Only DL themselves can tell you if a flight is actually oversold. The "seats" you still see for sale on such tools like Expert Flyer and SeatCounter may include the overselling seats so there is no real way to tell.

A lot can happen from several days out so it is way to early to predict. As lls138 said, get there 1.5 hours early or call DL 2 hours early. They will know better then.