Most schools have a formula of acceptances offered to those that actually matriculate. That's the whole point of having a wait list. When offered an acceptance and you politely decline, that means an individual who truly wants to go to the school now has the opportunity to accept. I've only applied to schools that I can see myself going to. This year wouldn't have been a good time in my life to start medical school and majority of medical schools understand that. Some offer deferment of a seat for the following cycle. If you're applying to a school and for some reason they ask why you didn't attend a school after being accepted, which they wouldn't, just be honest.
With regards to waiting another year, I've talked to dozens of physicians and every single one has said how they wish they had taken a year off to work or just to have down time. It's not for everyone, but it's also your career. What's another year? Once you go through the application cycle and talk to admissions administration, you'll see what I'm talking about. They want students passionate about their program, not someone accepting just because they need to start medical school right away or it's a backup school.