According to Christopher Smith, who would know, San Diego Chargers' Offensive Coordinator Clarence Shelmon will not return to the team in 2012 and it sounds like he's done with coaching in the NFL completely.
Since the hiring of Norv Turner, asking people who the OC of the Chargers has been a fun trivia question. Shelmon went so unknown and unappreciated because Norv Turner was the one calling the plays, but Shelmon had plenty of control over the San Diego running game (including back in the LaDainian Tomlinson days).
With Shelmon and Greg Manusky gone, the Chargers will be starting 2012 with two new coordinators (which they haven't done since 2007) and still need to replace the Linebackers Coach position as well as a few others that will seemingly come open in the next few weeks.
Look for the OC position to be filled with another Running Backs Coach, either on the team (Ollie Wilson) or otherwise (Jerald Ingram?), so that Norv can focus on Philip Rivers and the passing game.