I agree, after getting the joint degree email, the peace I had made with not getting an interview invite deteriorated. I called the admissions phone number and listened to the recorded message about interviews. It says that interview invitations are currently being extended, and they will continue to do so through the decision date of March 27th.
Everywhere else (including a previous poster who called and talked to someone, I think) said interviews are extended til 1-2 weeks before the deadline. I'm not sure what to think, but the optimist in me wants to hold out a teeny glimmer of hope.