I'm guessing that you're ranked when your on the waitlist, most schools are on a ranked system...Depends if your on the high waitlist or middle to low...High waitlist you have a good chance of getting a seat if someone declines, mid to low you have a poor chance...Depends on how they rank you and how many applicants they waitlisted before you and how many accepted applicants actually decline their acceptance..
I would call and ask them in regards to your position on the list..Good luck!