I'm not on the adcom so I'm not sure, but I would say it's likely that all the candidates they're most interested in have been interviewed at this point.
At this point it's likely that all a-list applicants were called on the 21st, especially anyone who indicated that they were applying to other schools so IDM doesn't loose them to a competitor program.
Anyone accepted from this point forward is likely on the b-list - a pool of applicants to pull from should anyone decline their offer.