From the recent Lorne N' Stewart AMA;
LorneLanning 3 points 8 days ago
"We are encouraging fans to send voice samples of characters they would like to do. If they are great, JAW would like to talk to you about characters to do. Oddworld has always done its own voices, and hopes to keep the tradition in the fan community. Some fans just happen to be famous actors... but that will be announced later. Is way cool when this happens."
From OddworldInc's Twitter;
@simonpegg So, how do we get in contact with you outside of the twitterverse? We'd like to ask you something. 
So, Mr Pegg confirmed for voicing a Mudokon yeah? :P