I interviewed at BU on Feb 13. They told us they had a good amount of seats open (forgot how many, sorry) and that they were still planning on interviewing a few hundred more students. They also told us to be patient and allow them 4-6 weeks before we got a response. Then he smiled and said, "Maybe even longer."
So there definitely are plenty of seats open, but they definitely are planning on interviewing a lot more applicants!