Amazon has begun listing a November 19th date for Yen Press' release of light novel collection The Surprise of Haruhi Suzumiya, the finale of the series as it currently stands. The English localized will package the two Japanese books in one hardcover for $18.00
From the description
The Haruhi Suzumiya Series comes to a close with this tenth and final adventure for Haruhi and the S.O.S. Brigade.
The two storylines from The Disassociation of Haruhi Suzumiya continue, introducing a new inductee into the S.O.S. brigade who may be more than just the eager freshman she appears to be. As the two realities converge, the SOS Brigade learns that the new member may have the ability to bring the two story "timelines" together-and save the world in the process.
This book was originally published as two separate volumes in Japan, but the U.S. version will feature both volumes for the price of one.
@ultimatemegax translated a relavent bit of 2011's The Observation of Haruhi Suzumiya (novel fanbook) concerning further Haruhi books...
Editor 1: This is a fanbook we've arrived at after much trouble. Wouldn't it be alright for all 5 SOS Brigade members to appear on the cover...
Author Nagaru Tanigawa: Won't people say "Those guys again?"
Moderator: (laughs) How about the poster be (novel 9/10/11 characters) drawn by Ito? Why not use the SOS Brigade image in the next volume?
Editor 2: How would that represent the novel...
Tanigawa: I've not sent the plot to the editors yet, but I've begun writing. I'm writing, but I may throw parts out mid-way...Alright, how about I tell you verbally now?