I think your course of action is sound. For the most part, if you haven't heard by now, you're in the rejected pile and will slowly have snail mail letters of rejection trickle in from now through April (I got one in August last time I applied!)
However, it has, very rarely, happened--that is, someone will get an offer without hearing anything up until the very end and without interviewing at all. One of the students I spoke with at University of Montana said that his POI called him April 15th and said something to the effect of, "you were the next in line to get an invite to interview, but I was only allowed to invite 3 people. All 3 of them have declined. Would you like to come to Missoula? Sorry for the late notice, but I can only give you an hour to decide and then I'll need to move on to the next person on my list." He replied that he'd love to come to Missoula, and has done quite well. This is the only time I've heard of something like that happening, myself, though.