Out of the 1844 applicants, only about 430 have received at least one MD/PhD acceptance, but most of them have multiple acceptances. By the end of the cycle, we should at least 300 more applicants getting MD/PhD acceptances. As a quality applicant, you should be fine. I have had several accepted applicants into my MD/PhD program who have received a top 10 MSTP acceptance (from their waitlist) as late as the first week of May. I suspect that your chances are very good (2/3) if you are waitlisted by 3-5 MSTP programs, and extremely good if you are waitlisted in a greater number of programs. A couple of years ago, I saw a kid holding two acceptances until the very last day (April 30) in the very top programs, over the next week, the domino effect fell with several other applicants getting acceptances...
This is very frustrating to applicants and program directors (most of whom are trying to keep steady enrollment numbers due to limited resources). The best thing for everybody would be to have a match system similar to what people do for residency positions, or as it is done in Texas, for Texas residents in state-funded medical schools (MD program only and in TMDSAS; for Texas MD/PhD programs, state of residency doesn't matter and applications are in AMCAS).