I just read a report that the ash column at Chaiten is beginning to collapse. The SERNAGEOMIN says that the ash column is only 4.5 km tall now, as opposed to the 20 km it had reached earlier. Still, there are not reports of pyroclastic flows, but that could be a matter of hours or days at this point. We'll be keeping a close watch on the eruption to see if this is the beginning of the end, or just a lull in eruptive activity, here a full 12 days into the eruption.
UPDATE 12:20 PM (Pacific Time): According to this new article, the SERNAGEOMIN is reporting the first of the column-collapse pyroclastic flows coming down on the edifice.