No way of knowing for sure, but certainly people do cancel from time to time. And sometimes people do not show up for their ADR without calling to cancel.
Keep trying every day, even after you arrive at WDW.
People do cancel them, I did and then tried later only to find that the closer it got to my trip it was more difficult to get. Keep trying you never know, it might open up.
I agree to keep trying. I have been very successful with this in the past. If you want to eat there bad enough you will just need to be persistant. Good luck !