Looks like the WLs are pretty prevalent today. Keep in mind:
1) The school historically has had a sub-50% yield rate. Yes I'm sure it wishes that was higher but at the same time I feel it's a testament to how many really bright students apply to Duke.
2) Duke's pretty much the first R2 school to release decisions. Later this month when some other schools release their decisions, some students will start to send back their cards declining admission.
3) If you look at the wait list stats for Duke on GClub from last year, a lot of the WLs later became admits
So there are definitely concrete reasons for optimism guys!