Sorry to disappoint you but no,
Goku Sayonara Zetsubou Sensei isn't the 3rd season you think it is.
Wiki wrote...
On July 8, 2008, the production of a third set of OVAs titled Goku: Sayonara, Zetsubou-Sensei was announced. The first volume was bundled with the limited edition of volume fifteen of the manga as a part of Kodansha's OAD Project and was released on October 17, 2008; the third volume will be released with volume sixteen of the manga on February 17, 2009.[3] The second volume was released as an original video animation on December 10, 2008.
So basically, it's just a 3 episode OVA/OAD, and not a full length season sequel. (I believe the 3rd ep was just recently sub'd by gg) - just look it up at
tokyotosho.com
and after you've seen it, might as well make some comments in this thread:
https://www.fakku.net/viewtopic.php?t=15827
...
now that I remember, I haven't even seen the first episode of it yet. :roll:
(MOAR Marina Inoue & Yu Kobayashi!) :D