THR.com has word that the next possible candidates for the business end of a knife are in discussions to join the cast of Scream 4: Lake Bell, Ashley Greene, Hayden Panettiere and Rory Culkin.  The production is reportedly looking for a July start date. 

Scream 4 reunites Wes Craven with Kevin
Williamson, who kicked off a horror- movie revival with his
Scream
script in 1996. The story brings back original cast members Neve
Campbell, David Arquette and Courteney Cox, though the new flick is
seen as a passing of the baton to a new generation of slasher victims,
with Williamson already under contract to write a fifth installment. 
If deals are concluded, Greene would play Campbell’s cousin Jill,
essentially the heroine of the movie, and Panettiere would play her
best friend, a nerdy film geek. Culkin would play a potential love
interest for Jill.  Bell is negotiating to play a police officer who
knew Sidney (Campbell) from high school.

Craven and Williamson are trying their best to keep the plot under wraps, including not even sending out the script to agencies, rather only character descriptions.