More on the Milingo mess
True, formal imposition of an automatic suspension carries a few consequences that merely latae sententiae suspension doesn't (see 1983 CIC 1333), but practically speaking these differences are minor and are likely of no significance for someone in Milingo's place.
So what is the "threat" in Cdl. Re's letter? Well, maybe Re is paving the way for a higher penalty such as excommunication to be imposed under Canon 1393 (for those who ignore lesser penalties). Milingo certainly seems to be providing as much provocation as he can for Rome to react sternly. Or maybe (and I admit this is, historically speaking, a long shot) the cardinal's letter is laying the groundwork for a flat-out dismissal from the clerical state under Canon 1394, the penalty Milingo would likely be facing if he were only a presbyter.
But alas, why get everybody's hopes up?
Updates: A good statement by Abp. John J. Myers; more thoughts from Jimmy Akin.