I would not be surprised if adcom meeting dates shift. Harvard BBS traditionally meets after the new year, but this year it was moved up to mid-December. It kind of depends on what the administration decides is best for the given year.
I believe Harvard BBS only sends out one batch of interview invitations. There may be a few stragglers, but that number is a very small percentage compared to those sent yesterday. To those who were not, commiserations. I am sure you will get into other brilliant graduate programs and wish you the best in your graduate career. To those who were invited, congratulations! I look forward to meeting some of you when you interview in February.