Professor Heinz Giegerich has pointed out to me that in the wake of Pope Benedict's resignation of his position at least two BBC reporters have been referring to the next pope, whoever that might be, using singular they. I don't have specific word-for-word quotations, but (apparently) reporters have been using phrases like The next pope will find that they…, or Anyone who expects the cardinals to elect them, and so on. Further evidence (to be added to evidence like the case of "They are a prophet") that singular they is not motivated solely or necessarily by ignorance or indecision about which gender is appropriate. The next pope, whoever they may be, will surely be a man, so the pronoun he would be appropriate and unobjectionable. But we have no idea which man, so singular they also feels entirely appropriate, contrary to what all the dumb usage pontificators say.
Neil Kelley (to whom thanks are due) emailed me to say that he heard what appeared to be another instance of singular they in a discussion of popes on NPR's Morning Edition. Curiously, in this case there was no ambiguity to either the identity or the gender of the pope in question (Celestine V). Nevertheless:
Linda Wertheimer: "Wasn't there a resignation of a pope whose name was Celestine, Celestine the fifth? What happened to them?"
"Them" apparently means "the pope in question, whoever it was". You can hear it around the 1:45 mark here.
Meanwhile Karl Narveson told me that he once got an email at work explaining the absence of an upper manager who was mourning the sudden death of his father. The sender was moved to share the following advice: "If you still have your father, be sure to tell them you love them."
It's all the same phenomenon: when the antecedent is similar enough semantically to a quantifier expression and the pronoun functions as a bound variable ("if you still have the X such that X fathered you, be sure to tell X that you love X"), singular they/them feels grammatically acceptable, even if (as here) in retrospect it is a little bit odd that it should be used in preference to he/him.