According to Weekly Shounen Magazine vol.21, the third season of “Sayonara Zetsubou Sensei” was announced to be aired from this July. The title is “Zan Sayonara Zetsubou Sensei”.
Staff
Director: Shinbou Akiyuki
Character Designer & Art Director: Morioka Hideyuki (“Sayonara Zetsubou Sensei”, “D.Gray-man”)
Production Studio: SHAFT
OP song artists: Ohtsuki Kenji & Zetsubou Shoujo Tachi
Source: Scan of Weekly Shounen Magazine
“懺 Zan” means confession.