I'd say they'll open with either ANTR and/or AROP, close with PMU, and have, at least The Mirror/Lie and/or WIMH/TTTSTA. As for what else, it'll probably be based off of what they've been playing, and whatever they might pull out during the current tour leg in Southern America. I wouldn't expect too many surprises with an hour-long set for them, and they probably won't want to have to re-learn songs they haven't been touring recently, so if it hasn't been played in the last year live, they probably won't do it.
Just, prospectively, judging by recent setlists, if they have an hour...
A Nightmare To Remember
A Rite Of Passage
The Mirror
Lie
Sacrificed Sons
In The Name Of God
6 songs, just a bit around an hour... and it would be KILLER. I think those are probably the best, heavy songs from their recent setlist, and SS provides a bit of a breather space for them (the first half at least), and closing with ITNOG would just be epic.
Although I do agree about them playing shorter songs to withhold the attention of Iron Maiden's fans, I don't think it'll matter, really, since songs like ANTR and ITNOG are sectionalized to the point that it almost sounds like 3-4 songs blended together anyway. I think that set of 6 songs would be a treat, and would make for a FINE live recording (then again, we already have SS and ITNOG recordings, but it'd be hard to pick anything else that's heavy and hasn't been released live by the band officially).
-Marc.