According to mmaweekly.com:
Anthony Pettis has signed on to face the reigning and defending champion on December 16 in Arizona in the main event with the lightweight belt on the line.
The news was confirmed by sources close to the fight on Thursday, with bout agreements already issued and signed for the December showdown.
Benson "Smooth" Henderson (12-1)
Win Donald Cerrone - Submission (Guillotine Choke) WEC 48
Win Jamie Varner - Submission (Guillotine Choke) WEC 46
Win Donald Cerrone - Decision (Unanimous) WEC 43
Anthony "Showtime" Pettis (12-1)
Win Shane Roller - Submission (Triangle Choke) WEC 50
Win Alex Karalexis - Submission (Triangle Choke) WEC 48
Win Danny Castillo - KO (Head Kick and Punches) WEC 47