I do this route regularly and it is not unusual for there to be just 2 of us in First until a day or so before departure when suddenly the cabin is close to full (although I have been the only passenger on one occasion).

This aircraft turned up for quite a few flights during the Winter timetable to IAD, my last 2 this month were showing as the 12F variety on booking but they were both changed to the 14F a month or so prior to departure ... and both had Thales!