He isn't going anywhere. They do this once every 4 to 5 years, and then he is rewarded with a 2 year extension about half way through the season or near the end of the season. It is like a self-motivation thing for Marvin versus anything else. He wants the insecurity to push him to drive the guys a little harder. I don't believe for one second that a 58 year old man making 4 to 5 million dollars a year is going anywhere, especially when he has such job security with Mike Brown.
He went into 2010 without an extension is well..... That year, he took a playoff team from the year before, added a former all-pro receiver and ended up winning 4 total games. He was rewarded with a new 2 year deal.
Marvin's contract has nothing to do with success.... The only reason why the Brown family would let him go is if he wants too much money or he's doing something behind the scenes to irritate the family.