The waitlist was not used in the past very much (I think like 40 people got in this year)
BUT
this year they have no idea what to expect for yield, etc, because half the class hasn't been locked in, as was the case with ED. So be optimistic!
Check out this headline:
With no early applicants, U. will draw heavily on waitlist - The Daily Princetonian
If you don't feel like reading it,
"Rapelye added that, because of this year's uncertainty about expected yield, her office will initially admit a 'conservative' number of students and then possibly take 'several hundred students off the wait list.'"
In other words, they will use the waitlist much more this year! Good luck everyone!
Edit: I'm a current freshman. If you have any questions about Princeton PM me!