The University of Arizona has always faced a difficult financial situation, with its tuition kept artificially low at the same time a slightly crazy legislature regularly underfunds the public system.   Among the publics with top PhD programs, I think Arizona has probably had the most trouble, although things have gotten more difficult in recent years in North Carolina with the takeover of rabid repugs in the state legislature.  I do think, ceteris paribus, anyone holding out hopes of getting in off a waitlist elsewhere would be well-advised to forget that (I strongly suspect many schools, even private ones, will decide not to go to their waitlists–or will be told not to go to them) and accept any good offer they have in hand from a public university.   The fact that one major research university, Arizona, has pulled financial aid from outstanding offers may inspire others to do the same thing.   Do note that the Arizona financial aid offers did, as Professor McKenna notes, come with an "escape clause" (offer conditional on funding availability etc.), so if your admissions offer did not include such an escape clause, you probably have less to worry about.

ADDENDUM:  Just to be clear, there is no reason to think UNC-Chapel Hill is thinking of revoking any financial aid awards.   I was only giving North Carolina as an example of a state with a crazy legislature in recent years!