I'm going to wager that it's Tora's death (again) that drives him over the edge. Wasn't she one of the super-heroes who "cheated death" in the previous months solicits.
Also - James Robinson will be writing the JLA Blackest Night tie-in (for those who love "WEEP FOR JUSTICE") but he'll also be writing the JSA Blackest Night, which is very interesting since it was Robinson along with David Goyer who relaunched the modern JSA title and his Golden Age and Starman work is still regarded as classic/best stuff he's ever done. And he'll be bringing back Wesley Dodds - who he killed off. If Robinson wasn't so determined to keep Jack Knight retired this would be a perfect spot for Jack to face his father, his brother, and Myst (both of them). But I doubt we'll see it happen - Courtney and Pat Dugan vs the Original Star-Spangled Kid though I think is a cinch. I wonder which Robinson will turn up - the Cry for Justice one or the Starman one.