I recently learned that the Close of Invitation (COI) has passed at the post for which I was nominated. A Peace Corps staffer informed me that this means I probably won't leave until January at the earliest.
So why didn't I receive an invitation to serve at the post for which I was nominated? I don't know. It seems possible that I delayed too much in submitting my paperwork. I was nominated in February and didn't complete the medical application until nearly July. It seems possible that by this point they already knew who they wanted to invite.
Another possibility is that my Placement Officer didn't feel I was as good a fit for my intended position as my recruiter did, or maybe there was an even better fit for me at a post accepting invitations in early 2011. At any rate, I originally expected to depart in October, which means I have three or four months more than I expected before I leave.