Hello,
I was also waitlisted at Rice for the biosciences program, and I wondered the same thing, "what are the chances of being admitted off of the waitlist?" I too have yet to hear anything back, but when you think about it, they'll probably make final decisions after all candidates accept or decline the extended offers. It would be nice to know if they rank waitlist applicants, consider all waitlist applicants by hosting another round of interviews, or if they just directly admit certain candidates. It's so confusing and perplexing, and I know exactly how you feel right now.