The way I approach hold situations is this: if its a low yield school (GWU, NYMC, Georgetown, to name a few specifics) then I would assume a rejection unless told otherwise later on. At the same time, I am pretty sure that there are some schools that just hold practically everyone decent at the beginning of the cycle and hand over very few interviews initially (typically URM, stellar stats, alumni, etc) and then open them up after they see more of the applicants for the current cycle, including many of those initially on hold.
I understand that some people will argue that on hold isn't a rejection and that applicants every year go from being on hold to interview invite later in the cycle. Although that may be true, when a school has 10,000+ applicants and only like 750 interviews or less if you don't get an interview invite after the first look of your application, your chances probably go way way down (and in my opinion non-existent at certain low yield schools). And a couple of positive sdn anecdotes doesn't exactly excite me about my chances as an applicant on hold at these schools lol.