Good one Bernie.......
Off the top off my head I'd say the tag question is as follows:
mustn't he have?
However, that does sound a bit awkward doesn't it? Especially in American English. It raises another interesting question regarding tag questions though. What would be the tag for this one? He's sure to have gone home by now.............? To say, "hasn't he" as the tag for that one sounds a bit awkward also.
I think though that in spoken English we can deal with the situation through the reliance on proper intonation and simply restating the question as, "He has gone home, hasn't he?" In this manner we can stress or pitch the word "has" in a way that implies the same meaning as we wish to imply by using "must have" or "sure to have."
In the rare situation that we would write such a sentence, it would be informal writing and therefore fairly unrestrictive; however, again, I think we could rewrite it in a less awkward way.
Well, that's my take anyway. It would be nice to hear from some of you true grammarians out there.