This is from wikipedia and we all know how accessible the site is to wisecracking fakers so before I give my two-cents on this one, I think I need GossipCop to validate this or whatever. Though, for starters, I really think Kristen with Zac Efron will be "interesting".
As of March 16 GossipCop clears that Kristen has not finalized anything regarding this film.
"Backwoods is a 2011 disaster film-action film, based on the 2012. Backwoods will star Kristen Stewart and Julianne Moore and be scheduled on August 12, 2011.
In November 2011 in LA, Bree Thompson and her mother Anna have moved to New York to live a new life when Bree meets a guy in the school named Alex who tells her that the end of the world will be in December 21, 2012 and is very close.
* Kristen Stewart as Bree Thompson
* Julianne Moore as Anna Thompson
* Zac Efron as Alex Royce.
source via fiercebitchstew