I think you answered the question, Garth. Teams have until 4 PM EDT today to make the cuts---and while some of the Cardinals' cuts have been leaked through Twitter (most likely because the players' agents want to get their clients' names out there asap), the Cardinals, as they always do, want to wait until they have made all the decisions in order to announce them collectively.
If you notice a number of teams that have announced some cuts, have trimmed down to 58 and still have to make 5 more cuts---like the Rams, for example, who at this point still haven't made a decision on Michael Sam.
Every team is hoping to trade players they are going to cut anyway...so...until 4 PM EDT the GMs' phones will be ringing fast and furiously. Wouldn't it be fascinating to be able to listen in on Steve Keim's phone calls today? I would bet he is already up this morning (5 AM AZ Time) and is already on the phone or making calls himself.