Mike Colter, the previous voice and face of Agent Locke, will no longer be providing his vocal skills for the role, but will retain the image.
Most people were not impressed with Agent Locke's voice in the Halo 2: Anniversary cutscenes, and it seems 343 Industries took notice of this, and have removed him from a vocal role. This comes from Ike Amadi's Twitter.com and his IMDB.com page, where he has confirmed that he will be doing the voice for Agent Locke, but Mike Colter will still be the physical representation. Rooster Teeth also allegedly live streamed an interview with Ike Amadi, where he talked about his new role. While 343 themselves have not been vocal on the change, multiple sources such as the ones above have confirmed that the famed video game voice actor will be taking Mike's place. Ike Amadi is known for his roles as Javik in Mass Effect 3 and miscellaneous roles in other games such as Call of Duty: Advanced Warfare.