Please seriously consider cancelling interview spots that you've been holding on to in the hopes of a swap.
At this point, there's still time for the programs to give January dates to applicants on the waiting list, think about the fact that they could need the spot a lot more than you do, even if you could conceivably make it if you happen to hold out long enough to get a swap.
Being a no-show reflects negatively not only on you, but also on your school. So you're not just keeping prospective colleagues from getting an interview spot, you may keep next year's applicants from getting one, too. It's also just a rude, inconsiderate thing to do. So please don't be that guy. Leaves a bad taste in my mouth when I see that last nametag sitting there and nobody comes to claim it.
I had to cancel an interview that I actually wanted to go on, but conflicts happen and they aren't all avoidable. Please be responsible about it. Thanks everyone